If you replay, which you have to reach 60(possibly twice), you can save Wrex. Or you could use a little glitch on Noveria. Also I was unaware of you doing this, or else you would bet, I would have told you this stuff at the beginning. Also the glitch http://masseffect.wikia.com/wiki/Morality#Infinite_Paragon.2FRenegade_Points_Exploit
Psh... Wrex provides great help in ME2, and ME3, even if you can't make other certain choices without a major consequence.