To be completely honest I don't even know if you would have to stick to real world physics, I think you would beause your real body would be under their effect and you would feel that and thus your brain would translate that through to your avatar character. But on the other side of the equation if your willpower is strong enough you could theoretically "force" your mind to ignore all but the game, thus making it so you could pull Neo's "superman thing."
As for your idea, that is straying into a very grey area I think, one the technology doesn't exist yet (if it ever will), and then there is the idea of copying your mind I.E. your soul thus making 2 of the same person. Personally I like being me and the only me.
Also to kinda be on topic, the "Other" catagory is winning over both Loli and CHF, that what I voted for (I only have one female childhood friend and she is married). and if you look in the Post One Ecchi Pic A Day topic you'll see my thought on lolis