I think I've got a possible algorithim for .sexrepro (I know you get this a lot, but hear me out).
1. Check to make sure that both bots are of same species. If not, insta-fail the sexrepro.
2. The new bot should be created with the original, unmutated DNA.
3. Compare mutation histories of the parent bots.
4. If the two bots share any identical mutations (AKA, a common ancestor, or perhaps random chance) apply these in the order they were formed.
5. Randomly select some of the remaining mutations from each parent to be enacted.
6. Parent one's selected mutations should be enacted on the new bot in order.
7. Parent two's selected mutations should be enacted on the new bot in order.
8. New bot is free to do whatever the hell it wants.
An example:
Base DNA:
cond
*.nrg 100 >
start
50 .repro store
stop
Mutation Histories:
Parent 1: Del "cond", switch "*.nrg" "100", del stop
Parent 2: Del "cond", insert 50 at end, insert 12 at beginning
Possible New Bot DNA:
12
100 *.nrg >
start
50 .repro store
stop
Obviously, that's a simple example, but you get the idea.