It depends on the origin-story that they're going with. In the G1 comic the ability to transform was an inherent ability of their species, not a later developed ability like in the cartoon.
When I was a kid I had no idea what the hell Mainframe was supposed to transform into (it's not like I'd seen that many mainframes at that age). I think it'd be neat if he did transform into a computer - especially if he's going to be a non-toy character, since marketing (and thus alt mode choice) wouldn't need to be factored in.