Something about directly augmenting the ability to write to and/or retain long-term memory?
Improved mental acuity, so that we can better analyze and understand in the moment? It's easier to retain things that you more fully comprehend.
Something about an emotional intensity booster, to tie into the emotional triggers on learning?
Something to directly improve mental resilience in a way that would allow us to focus more intensely and for longer without running into fatigue/burnout issues?
I'd think implants, but... if we're planning on developing a T5 implant base to best exploit the second contract, I kind of want to wait on actually pushing the transhuman thing all that far until we have it... especially since we'll almost certainly be specializing it for "stack on lots of implants without negative side-effects".