Can't remember where, and from who I heard it from but there's a MKIV running with Brembo 14's in the front and the stock fronts in the rear. Sounded like a good idea so I thought I'd see what was involved in the swap. Didn't think about the e-brake thing either.
You will probably need a larger master cylinder to support the added caliper volume if you did the swap you mentioned. You may also have problems with wheel clearance when installing the front caliper on the rear.