(I was gonna reply to the previous thread but after writing all this I felt it seemed more appropriate for a standalone thread, it's a long read, here's some music: https://www.youtube.com/watch?v=hFxCDbiPWJk)
I have noticed that people, especially solo players without a strong guild to help them farm bosses, have had some negative feedback about the current promotion system.
Personally I think it helps make the game unique. I feel that if changes are made to greatly alter the current system it would feel like any other generic MMO and not the unique gameplay style that SS has conjured and mystified me with so far. Furthermore I say keep 25 and 40 because when I see a sub-60 Jonin I think "Woah, thats a badass" and the idea of a 40 Jonin obliterating a level 60 "Super Genin" is simply cool and fun.
My input is this: The current system, while slightly painful now, will be incredibly fun and rewarding once some major content patches are introduced. Instead of simply doing your dailies and grinding there could be other ways to gain 2-4 D or 1-3 C slips per mission. These missions would focus around infiltrating a rival nation and other similar concepts.
Infiltrate a border nation:
Kill an opposite faction player of the same rank, the target could be randomly generated from a list of same-ranked individuals in the pvp areas of the zone.
Steal a precious item; an item would be placed in a certain area. Host nation shinobi could be rewarded slips for killing foreign shinobi in the vicinity of the object (a large building, ruins in an open field, etc). The item is removed from your inventory upon death (perhaps the "item" could actually just be a buff that dispels upon death). This would also serve to create PvP hubs for lower level/ranked players as currently there is no real lowbie PvP outside duels.
Questlines that open up access to "neutral" merchants in enemy territory. This questline could take you all over your host nation and then on a tour of the enemy nation. At the end you get slips/boosters and open up access to banks/vendors etc in isolated areas in the foreign nation (outside of the main hub of course). Because of the risk involved I think this would be fun and rewarding. To prevent griefing of this mission you could implement a choice of 3 quests that all reward the quest item needed to progress to the next quest. That way it isn't just one NPC everyone knows that a lowbie will be going to visit so it isn't camped.
Custom Deliveries:
A couple of quests focusing on crafting an item of considerable value. This would not only be a natural way to get players into the professions but also serve to stimulate individual economic accountability and prevent the desire to purchase ryu that may arise later on when the game is more popular and people become tempted to do so.
The item would be turned into an NPC in exchange, for example, for 4 D slips. The item must have been crafted by the player. (perhaps this would be easy to implement as the crafted by tag system already exists in wow).
Not Spammable, you can only do it a time or two but for a worthwhile number of slips.
Environmental Challenges:
Shinobi Story has THE most fun movement I have personally experienced in an MMO. I think this should be capitalized by adding more movement related challenges. You already made a brilliant one with the water-walking jutsu challenge.
Jumping puzzles would be fun and relatively easy to implement (do I sound like a moron for saying this phrase again and again with no knowledge of the work involved to actually implement any of these suggestions? probably)
Speed challenge; a player touches a monument and is given a 60 second buff. He or She must race to the next monument along a path, this renews the buff and adds a stack. Reaching the required destination with [x] amount of stacks while the buff is still active will reward slips. Perhaps an EXTREMELY challenging route could be created that would upgrade your movement charges from 2 max stacks to 3 max stacks. I think this would have to be very difficult and skill based however because obviously movement charges are quite strong for PvP.
Using the already implemented unsealing scrolls, add a different version that is rewarded by doing challenges that could open a different colored glowing orb in rarely visited areas, this would help reward exploration.
1v1 Arena:
Since the Chuunin exams are so spaced out, an arena bracket strictly for certain ranks could be implemented to allow players to gain slips via PvP. To prevent wintrading either slips would only be rewarded for a victory over a certain MMR (2k+?) or would be given out at the end of each week based on MMR or W/L ratio. I think this could be very-hands off with the GM staff if the pvpers have a form to easily and objectively report anyone abusing the system. I think this would be a big hit as 90% of good PvP players I have met in MMOs absolutely hate grinding and just want to jump into PvP but ironically also dont like systems where a fresh character can enter in and get on the exact power level as a veteran character. I think this would appeal to their desire to both gain power through PvP while also feeling like they actually had to earn the power they have.
Of course Open World PvP is more fun and immersive than instanced arenas but creating an environment that presents fair fights would be a daunting task IMO.
(Perhaps in these Arenas the player is not playing as themselves, but canonically as another person so they could customize their mastery in the waiting room to try out different stuff and make people not feel forced to pick a pvp heavy mastery when they are mostly going to be doing PVE).
Spawns:
To prevent super guilds from completely barring casual players from bosses I think some challenges or through some other in-game system could reward an item that, when used, spawns a boss similar to the bear or the Notchi beach crab. Solo players would be encouraged to make friends so that they can get use out of the rare item they have found because the boss is not soloable as genin. The user gets to loot the slips and the helpful players get a decent amount of EXP.
Small nations:
When the small nations inbetween major nations are implemented there are a variety of unique activities that could be present inside them.
Supplying the rundown residents of a minor nation with crafted food, raw ingredients, crafted medical supplies or raw materials farmed in the world, (similar to the existing already coded event of the AQ war effort from WoW) except on a smaller scale and more frequently, also you would be in competition with other nations to see who completes it first. Proper completion of the task would reward those who submitted items to the cause with spawn items or the proposed unsealing scrolls all the way up to pure slips or Koban based on the amount they contributed to the cause. This would also be a good ryu sink to combat inflation while rewarding crafters for crafting otherwise less marketable items.
Kinda Stupid Ideas: (read with a grain of salt)
To my knowledge the only way to find out what a player's masteries are is to either ask them or witness their abilities/buffs/lastname. Perhaps you could be rewarded minorly for properly inputting the 3 masteries of a jonin player you witness from a neighboring nation, I think this would encourage a fun minigame of stalking an enemy jonin and spying on them like a true ninja. However this system could be easily abused by other players creating databases so its in the stupid suggestion.
Art; a section of a wall or some such thing in a village could be set aside for implementation of world-appropriate fan art on a weekly or monthly basis, would encourage community involvement and also be cute and unique. The artist could be rewarded 50 slips or something to make it worth their time.
KING OF THE HILL: Free For All PvP area sorted by rank where players use their movement charges to try to stay on an area that is constantly doing knockbacks, slowly or other movement impairing effects while making it difficult for players to stay in an area/alive.
Clearly it is no easy feat even now but I think for longevity of the game getting S rank should be an unimaginable grind, similar to getting level 66 in BDO: attainable but incredibly rare. If not that maybe adding a rank (that isnt crazy powerful like the jump fron chuunin to jonin) past Jonin that is only rewarded for being an outstanding player in the game: becoming a Kage, becoming a server legend, having a huge influence in the RP scene etc. This would probably be very controversial I realize but at the same time I simply think its neat Also I think it would help prevent burnout from crucial members of the server(s) that help keep the atmosphere of the world alive.
If it isn't too much work, having NPCs greet you with different text for achieving Chuunin or Jonin would be neat.
Something like ninja dogs which you could summon that would simply give you the wow abilities: track humanoids, track animals etc. Clearly not on the minimap which is now the compass but instead maybe as a custom addon that just pops a little pseudo-minimap tracking square with no features except for the icons of the tracked npc/players.
Lastly but most importantly; buff my mastery.
Thanks for reading, I could rant more about all the things id love to see in this game but I think ive made you, the reader, suffer enough.