Tried it and had no success. IIRC you need "UNITTYPE_Factory" to build units, and giving a unit "UNITTYPE_Factory" makes it immobile.
Ditto. Tried to make the air factory be in the air once. It always starts on the ground; without UNITTYPE_Factory it could take off and seeing it fly around was kind of cute. Point to add is that it can build units, but they get built at a specified point, like when the orbital fabber used to build mobile satellites. With UNITTYPE_Factory, units can be built inside the unit, but all orders go to the units being built instead of the unit itself. For this to work, you'd need a way to distinguish orders for the factory from orders to be given to it's products.
I'm also looking into this, because I want to bring the Nuclear Sub online to add more variety to nuke and naval play.