No. Just No.

A society of rational agents ought to reach the conclusion that they should WIN, and do so by any means necessary, yes? Then why not just nuke 'em? *

*replace 'nuke' with whatever technology is available; if our rationalist society has nanobots, we could modify them into something less harmful than barbarians.

Offer amnesty to barbarians willing to bandon their ways; make it as possible as we can for individual barbarians to defect to our side; but above all make sure the threat is removed. That's what constitutes winning.

Turning individual lottery-selected rationalists into "courageous soliders" is not the way to do that. That's just another way of losing.

Furthermore, the process of selecting soldiers by lottery is a laughably bad heuristic. An army of random individuals, no matter how much courage they have, is going to be utterly slaughtered by an army whose members are young, strong, fast, healthy, and all those other attributes. If the lottery is not random but instead gives higher weight to the individuals best fit to fight, then it is not different from the draft decried above.

This is a terrible post, the first one so awful that I felt moved to step out of the lurkersphere and comment on LW.