Well, I'm not sure you could have a general as an individual (without having lost the rest of his bodyguard in battle), and I don't think you could really modify their stats yourself (perhaps further clarification is needed in your suggestion).

You can certainly use your general to flank the enemy, and generals are already a great unit to use as reinforcements for the rest of your troops.

I hope that answers your second point at least. There may be some way to introduce an RPG like levelling up and skill-selection system, but I'd be a bit surprised.