Personally, the best theory I have seen is the one someone posted that had the idea that two of the bikes form into armour and weaponry. This solves all the problems with any of them being destroyed thus making transformations into a combined robot mode impossible. Also, this idea is good because it means Arcee still has added height and bulk but if the "drone" bikes are wiped out she can still transform into the basic robot form without trouble.

 

I'm with Skowl on this one..was thinking the same thing.

A bit of a shame, I was kind of getting used to (and affected to) the unused movie1 / toy design.. but I'm interested in seeing how the three bikes will end up working.