I previously apologize for my possible bad english.
Okay! There's some features that I've already implemented in the game I'm developing, spiced with a few ideas. (The game is a RPG, btw.)
-Active Time Battle: I just love ATB system, because I feel it boosts the "battling experience" in an RPG. It forces you to think fast and to react almost in real time.
-Combo system: It is simple. When you attack with a particular skill, if it has the chance of "combo", it will activate a timer where you must press a particular combination of buttons to make the combo skill. The player must discover every particular button combination through gameplay, in a trial and error process. Also, the number of combos that a skill could have are undetermined. (You may discover which is the max count for every skill.) And that's not everything, combos are not just "hits", so they can have a deep mechanic in tems of "effects".
-Skills: You simply aren't going to learn new skills through leveling up. You CAN level up some skills —or combos— by using them. But to learn new skills, you must find Masters or data you'll get in your adventure.
*Skills learned through data are potentially the ones that can be leveled up more times, but they start being disastrous.
*Some skills are paid with blood. —What do you think that mean? I'll speak about that in the future— =P
-Level: There's no player level! Or maybe there is...? You can level up, like in almost every rpg that exists. But here is the difference, you CAN'T get "experience". You can train your stats in a very different variety of ways —with a limit per level—. So, how's the "level up" working? Because, when you level up, your stats increase all together, as normally happens. The thing is that you can ONLY level up by defeating bosses (and there will be a bunch of hidden bosses).
And that's all for now, keep save your hair!