No levelling, you can raise individual stats by using them, but each stat increase is harder to get. You can unlock traits and skills to influence your play style with quests or hidden conditions required to unlock them.
Each player would have to manage
• HP
• Stamina
• Mana
Classless play. You can self-identify as a certain few classes, and NPCs can comment, but for the most part, it's free rein.
A for Honour-based directional 6-sided combat cursor. Magic can work the same way with the circle expanding when casting spells that require being aimed, as some can be homing. It would make combat a more skill-based affair. Your skill level with cerian weapons or magic could affect this as well.
Unique items and skills, as well as traits for rewards, so players can compete and explore for hidden secrets.
Every time one of your stats raises, it gets harder to raise, but also every other stat gets a tiny bit harder to raise. Using the stat is the best way to improve it, with different inputs being necessary to have it count. For example, strength will go up when swinging a hammer, but unless dodging, parrying and other actions one might take in combat are done, it won't count to a certain extent. Same for casting the same spell or casting it on the same person a certain number of times in a time frame.
You could pick a race, and that race would have access to certain skills and traits naturally. They could also raise certain stats and skills more quickly.
You can "sleep" in a bed and have the chance to keep or ditch the individual stat increases you have acquired.
A skill is a measure of how proficient you are at something, with many of them being acquired and improved through common sense. Using a sword a lot will give you a swordsmanship skill and improve it. There are passive and active skills. One, like swordsmanship, is passive, whereas another, like "Super Cutter," is active.
Players can only have a certain number of these Active skills equipped at a time. Passive skills you can have as many as you like, but the more Passive skills you equip, the slower they are to level.
Traits are things that can affect how you play massively and can be unlocked by doing various things. For example, if you keep running out of Mana and you hit rock bottom in the middle of a fight 100 times, then you could unlock the trait “Blood Mage”, which switches any Active skills that use Mana to using Health instead when you run out. Another could be “Wind Walker” If you keep dodging after like a 1000th time getting a close dodge, you could have dodging cost way less stamina and have it so you can dodge mid-air, but you take more damage if hit and can no longer block.
A very popular skill will probably be "sense", which will use the colours of the "aura" around a target to gauge its strength. Green means more than half of your stats are higher, orange means your stats are near the same and red means more than half of its stats are higher.
It would be a straight percentage increase if a weapon, skill or action required it.
Players could absolutely brick themselves when grinding. You can be a jack of all trades or a master of a few.
There will be items that are rare and can change the way you play or affect your character in certain ways. PVP will be a thing in some areas, and events like PVP tournaments could be a thing with certain items, skills and traits only available then.
Guilds will have access to certain amenities in their guild hall, such as trainers
Player-made weapons could have certain traits applied to them if the creator knows how. It would also allow for player-made gear to have a purpose that doesn't completely eclipse endgame gear.