Even more interestingly, and I'm not sure if I'm just missing this or not, but there isn't anything in the RPG that says you have to be of of the Aerospace Phenotype (obviously you want to be since the accumulation of fatigue is once every 3 years, instead of once a year, and the aerospace phenotype gives bonuses to certain rolls to avoid damage) to become a ProtoMech Pilot.
You have to have the Aerospace Phenotype when taking the ProtoMech Pilot Training Stage 4 module, but I don't see anything about it when looking at the Stage 2 Trueborn Creche Module. It could be somewhere else I suppose :)