(skipping capital letters & please forgive typos--typing lefty today)
yeah I would give that a hard thought. because think of an oreo cookie being an example of the tire cake--where the cake is the brown cookie and the foamor foam core is cut in the same shape as the oreo icing in the middle of coure. I would cover each 'cookie' separate w/ chococlay--and keep that baby chilly willy to get that stuff to set that cocoa butter asap--then roll out the piece of chococlay where-the -rubber-meets-the-road where the tread is on the tire--and you about eliminate/reduce your shrinkage from the blob of fondant
the-en you can smooth out the 'join' with the heat of your hand and also disquiose it in the tread design.
And you can make a superbly secure structure that you can deliver without worry--anchor that oreo icing section down into a foam base or whatever.
no extra charge for over thinking it for you 