Which would have a greater effect on endgame theory?

I'm not sure what you mean by Zugzwang being "gone". How would one get rid of it? 

this won't look good for your trial checkmateibeatu.

furtiveking- Zugzwang would be gone by letting both players pass selectively.

For one thing, if there were no zugzwang, K + R vs K would be a draw.

Well, zugzwang just refers to the situation that when it is your move you have no choise but making a bad move. There is no other option in the position. So it is a typical situation where a player resigns (depending on how bad it is of course). You can't remove that it is your turn to move. It would make no sense.

It would actually mean that a lot of games could not be won, because in a game where there is a forced check mate in a certain number of moves there will be a zugzwang situation before the check mate. The end game theory would need to be totally re-written. Actually the whole idea of the game would need to be changed. It would be extreemly difficult to win a game and rather pointless to play it.

the question is, how many mates are forceable without zugzwang? i know K+R+R v K is easily forced, but what about K+Q v K?

sure

Indeed

normally won K+P endgames would be drawn without zugzwangtoo

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Stalemate because it affects the classic K+P v. K endgame.

So does zugzwang.

stalemate is used in a far smaller amount of cases than zugzwang IMHO

I firmly believe that abandoning the Stalemate = automatic draw rule would create a much fairer game. Like it's handled in Chinese Chess e.g.

you're wrong. stalemate isn't used that much in real games apart from people blundering into it (thus it's their own stupid fault) but when it is used it's brilliant and shows that position is more important than material in chess and stalemate draws which are unavoidable are pure class

Don't know about class but my best result in chess came about in lightning chess where in a lost rook and pawn endgame I noticed that only my two rooks could move. I plonked one of the rooks down where it was en pris, my (good standard) opponent thought I had blundered and took the rook whereupon I kept moving my other rook next to his king for the couple of moves it took him to accept that his king could not escape the attentions of the rook and that stalemate was inevitable. Lightning is said not to strike twice but I would be sad to see even the remote possibility of something similar happening being lost. :)