Lots of people seem to remove these without too much issue. Will it weaken the frame, sure a little. The question is, will it weaken it enough to matter? How hard do you ride the bike? You'll probably see an increase in frame flex near the rear shock area.
Some people connect the rears of the top rails with a 180 degree bent tube. Make the parts and fit them up right, and any decent weldor can zap them together in about 5 minutes. Pay them in beer or something.
mystic_1