I have some ideas, but one I would really like seeing implemented at some time are skills that player chooses at the beginning of the game, after completing some special quests, after finding some scrolls, etc. Similar to Bard's Tale.
For instance, at the beginning player (Swordsman) could choose the skill to use sword and dagger at the same time, or Always Hit skill (which we have now at level 30), or the skill to get 20% more money when looting/killing monsters (or better yet, 20% more experience).
After getting to level 30 he can choose skill to throw daggers, use some special kind of sword (two handed, for instance, but with much better specs) or get better prices in shops.
After completing some special quest he can again choose one skill from a set of skills, one one which I would really like to have is much better crafting. So if a player is skillful at crafting (Blacksmith Skill) he could have a much better success rate (10% instead of 1% for certain items, 100% for others, etc). One other skill could be Potion Maker, which would give a player ability to make much stronger and better potions.
Oh, and flying skill would be fabulous! And teleporting beacons, like in Might & Magic!
This way we could introduce new types of weapons (daggers, for instance), special new items, and the game would be much more awesome.
