No need to fiddle with pick lists, just ensure that your mod uses the
existing "tank"mech inf" "leg inf" etcetera formations. Both coy and platoon, since the pick buys platoons on low points and so on. Ditto, sams, air strikes yadda.
Overwrite with your new stuff, but if you use the same formations then the existing AI pick list will use them. If you pit yours off in say the 900 series then your stiff will be somewhat unlikely to appear as the pick is using the old numbers and drawing blanks..
The AI pick list id extremely flexible, but also extremely fiddly to change if you aren’t us
and the info is available buried deep in some post(s) on the forum - I’m not even going to search for them. So stick to the existing formations - if the base OOb uses formations 123 (tank coy) and that uses formation no. 125 as its platoon - overwrite those and rearrange the template units as required.