it seems i erred on understanding the extra white die thing, it being only a representation, not an actual additional white die.
so far the options i see here as far as representing the transformitive qualities are
the system that swaps capabilities between forms, being essentially being three systems in one,(

/

/
transformation system), takes the space of one of the four systems. white die are untouched.
one of the white dice is taken away, and in its place the transformitive system sits, thus providing a hitpoint but no wild die roll.
the white dice are kept, but the frame can only mount three additional systems, with the fourth slot devoted to the transformitive system, with no die roll attached.
i like the first 'cause you keep all four systems and white dice, no fuss
second seems balanced but losing the white die roll is going to suck
third is growing on me, as it makes sense that a mech that transforms would not be able to mount all the doodads that a normal mech would, but also concerned it would suck when facing normal frames with maximum systems.
i also think its unneccesary to worry about what form the frame starts the game as or giving it a base form, shouldnt matter really.
still think only one system should swap between transformations

and thinking more on it, the only hard rule i can get behind for what systems a transforming frame should get is a motive system for the appropriate form, jet, hovertank, transport etc, as all the transformable mecha that i can think of had a form that was more mobile then the other.