It seems like this variant would make the turn order bid much more important! What do you think? Would it make it worthwhile to play El Grande with three players?
I don't think your suggestion is bad, it would certainly tighten up the game, but I don't think turn order and action selection are really the problem in 3p El Grande.
3p El Grande suffers from the same problems that plague most 3p area control games where either:
(1) the last place player plays kingmaker
(2) Player A and Player B go after each other and Player C coasts to victory.
For me El Grande is really a 4p or 5p game.