Imagine a game similar to WoW: a MMORPG in a vast world, questing, multiple class, levels, etc.
Only difference: NO GEAR
Rules:
-It must not be grindy, people doing endgame content are doing it to have fun.
-No gear, characters can level up, but there are no gear to grind, (if there is gear, they are only cosmetic with no stats).
-It must be diversified.
My idea:
Soft and hard level cap: As the game launch, the soft cap would be lvl 50 and the hard cap lvl 100. Every new level grants you access to new talents/specialisation. A lvl 50 character would be able to invest into 1/4 of his whole arsenal, and a lvl 100 into 1/2. Once a character reaches the soft level cap, he can still gain new level, but for each extra level, it would become twice as difficult to gain a new level, a second extra level would require three times the effort, a third would require four times the effort, etc.. Though, the soft level cap would be increased by one for every week since the game has launched. Hardcore gamers can rush on a single main character, and more casual players may prefer to level multiple alts or to wait until the soft level cap has increased further.
Game balance: For each ten level a character gains, his power would become twice as great. So a level 30 would be twice as strong as a level 20, and a lvl 40 would be four time as strong as a lvl 20. Health would increast even further, so as characters level up, fights would last for longer everytime.
Questing: Each race would have their own starting area, but most zones won't have a level requirement. Encounters would be adjusted to your level so you could quest wherever you want. Hence, a level 70 could quest in the same area as a lvl 20. You would unlock extra area as you level up, each of which will be more challenging the one before. While grouped, encounters will be adjusted to the level of the lowest character, though, players would only receive exp if the highest level character of the group doesn't exceed the lowest by ten. Quests would be random from day to day from week to week, and from season to season.
PvP: There will be no premade brackets, but each ''battleground'' or ''arena'' match would have characters within ten level of each other. To maintain balance, the amount of player on each team would be balanced based on the ratio of each side's character level. So one side could possibly have 10 lvl 70 characters while the other has 20 lvl 60 characters.
Scenarios: Each day there would be minor scenarios going around that would last for about an hour, but about once every week, there would be a huge scenario that would last for a full day. Some scenarios would be pre-programmed, but some players would be able to volunteer themselves to play as powerful monsters while the event last. Volunteer players would be rewarded depending on the amount of wreck they did.
Vehicules: As you level up, you would gain access to a wider array of vehicules, both ground and flying (and why not space ships). There could be vehicule PvP and races, vehicule scenarios, and zones dedicated to vehicules. Mounts may ruin immersion in WoW, but why not actualy increase immersion by using vehicules in a spectacular environments as more than just mounts? Individual races could even be created by player themselves.
Raids: There would actualy be no raid, but instead, encounters/scenarios that would tuned so high that it would require multiple players to defeat it. There would be no grouping or level requirement, instead, the threat would depend on the amount of players of each level bracket currently doing the event. Imagine a huge freaking titan that would deal AoE damage divided amongst the lowest level characters while focusing his stronger attacks on higher level characters.
Aesthethic: There would be no gear with stats, but there can still be aesthethic armor/clothing/weapons/accessory. Why? because people LOVE customization! There could even be player-made armors, clothes, weapons and accessory (each would have to be approved first to prevent abuse)
And the most important:
Player contribution: Why should only the devs be in charge of bringing new content? Players would be able to settle into their own instanced area, create their own encounter so that other players can actualy play those. Those encounters might provide few or no rewards, but most players would have fun trying out community stuff. Rewards could be given to the most popular player content. Each player would only have one instance each, but it could be as huge as the world itself, and they would be able to update it whenever they want. (Updating a player instance would reduce it's popularity to zero)