Some of these handicaps listed are just strange and would really alter the game of Chess. Yet it seems no-one has suggested one of the simplest and easiest-to-introduce forms: separate time controls (with the strong player getting less time and the weak one getting more time). I think this should be an option; draw odds would make little difference as even a difference of 100 points on this side means that the result will likely be win/loss. Therefore, I think the handicaps should be separate time controls, and then material handicaps (pawn, bishop, knight, rook, possibly Queen).
Instead of regular takebacks, here's a cool variation:
Once per game the weaker player can force the stronger player to take back a move, and move something else.
I reckon this can overcome a 300 point rating difference, the weak player gets some serious tactical opportunities if used correctly.