Two things I want to chime in on:
1. RTwP will necessarily wreck the rules
this is mostly due to initiative concerns. There was a game (with many other flaws) Called "Drakensang: The Dark Eye" (NOT Drakensang Online) that had accurate initiative and turn based combat in a RTwP game. When there were more enemies the turns became a bit longer, but all in all it was still very fluid and kept the order of actions correct at the same time. The only "flaw" was, that all actions had to be locked in at the start of the combat, and movement was obviously a bit skewed because run speed did not align at all with the duration of a round of combat. But for the base game (DSA in german TBE in English) the part about locking in all actions for the round was actually true to the rules.
Point is: RTwP can be pulled off in a Manner that does not necessarily destroy all other rules. The movement issue would be funny, D&D allows a nice amount of movement per Combat round.
2. AI for companions
I liked the gambit system of FF12. 'nuff said.
okay, not 'nuff said, here a little bit of explanation: FF12 had the usual ATB thing from Final fantasy going on, but they did remove the option of putting in all commands by hand, instead giving you some scant few slots of "Gambit" that you could fill with a trigger (ally below x%, leaders target enemy, highest magic power foe, etc.) and an action (cast heal, use item, attack, use special skill, etc.) and the AI always did the first thing whose trigger and action were available on the list.
It was a bit clunky, the limit on actions was always an issue as you needed to swap around the ailments you clear for some zones. And I'd like some more triggers (e.g. Friend has skill available for combo and is not occupied by healing) and ifs and essentially run my party entirely on some selfmade(!) programming. I know that is not everyones cup of tea, but it is mine.
ah one third thing: I lean more to the turn based approach myself.
1). Have you read Players Handbook? it states that its just a guide to be followed losely and that you should certanly change the rules to what you like ( making the game your own) And if you are a true DnD fan that actually played it with pen and paper, you should know that this is probably the most important rule in Players Handbook and of pen and paper.
EDIT : Why is my "Quote" looking wrong?