What would you say to allowing the Baktrians to recruit Pezhetearoi and other elite Hellenic units in all the provinces the Seleucids can? I think the Baktrian skin of this unit is fine looking indeed, it would make sense to have it available at least in Syria/Babylon/Seleucia. Also, how about allowing recruitment of elephant units for them in Antioch? Reasonably logical, and it makes sense to get as much use as possible out of such a fantastic looking unit.
In my opinion, with the logistical problems of the central Asian theatre, unit recruitment should be as generous as possible!
How difficult would it be to tweak recruitment myself?