Can't change Pioneers. They be hardcoded lad.
I hope this changes 
I loved 1 thing in the "Alpha Centauri" unit design module, that was you could design almost all theyre units (the only problem I ever found was getting the correct graphics on the "Probe Teams" (Spies), dont know if you tried it..
I think it would be great if i was able to give my pioneers the ability to see further, or boost units that defend them with more defense, or more movement speed.
PS, talking about that game, colony pods on huge ballistic rockets is the most silly way of building new cities ^^
Sincerely
~ Kongde