Maybe not entirely relevant to OP, but Ackbar isn't the only option vs Negotiator. Bugs work fine under Thrawn as long as Fives is in Negotiator's starting lineup. Fives will target Spy (assuming spy is weakest in your lineup), allowing you to almost 1-shot Anakin. Anakin will be saved by Negotiator. Then just wait until you can reinforce with an aoe unit to finish off Anakin. Battle is easy from there.
Probably isn't the optimal lineup, but it has a 100% win rate for me, so I haven't had any reason to look for alternatives.
https://youtu.be/s0_0MYy2UKk
https://youtu.be/UDwgBIGB3to