I wouldn't say sexrepro is a total loss. It does seem to help mix up the species dna somewhat. I've seen a bot with a bad mutation have it's children "cured" after a sexrepro with a normal bot. I've used it on plants and they started flying in opposite directions top/bottom so as to meet each other at the middle. It does however seem to crash the sims more often.
There could be a good reason the bots avoid some mutations. The bots are only striving for adequate mutations. If it takes multiple steps and one of the initial steps is detrimental it would be unlikely to evolve. The birth tie provides a guarantee that the bot will eventually seperate, a tie-removal gene requires that the bot tie then deltie. To deltie however the bot must use the same number, the most likely result being that the bot will not and instead of helping the tied mother/child will hender each other.
The reason why TF doesn't evolve is similar, it requires storing values into tieloc,tieval, and tienum. Shareing, however, can and has evolved since it only requires one number stored.
Shots probably are the best feeding method actually. The incomming shots come almost straight to the bot, they're in relativly small quantities that allow babies some chance of surviving. The bots can then randomly subtract 5/3 from the -1 and lose waste or gain body. Shootval could also have a num randomly stored into it to increase either range or power.
I'm trying to understand game theory so as to help figure out what gives the bots the best payoff evolutionary speaking. From what I can tell a sort of Retaliator bot would be the best for mutation sims. If it is attacked by a canni it responds in kind, if the neighboring bot is peaceful so is it. The only problem is ID between a Canni attack and an accidental discharge, and attacking long enough to have an impact.