Should be no problem with heating, you just have a bigger thermal mass which should keep the temperature more constant, not a bad thing.
I'm not a civil engineer, but I'd hope the cap would have some sort of reinforcing mesh in it. There are some amazing adhesives out there, so bonding probably won't be an issue, I'd just be concerned with the thin (for concrete) 2" cap cracking down the road, hence the reinforcing mesh.
On the up side, you now have a thicker slab which for mounting your lift and other equipment which is never a bad thing. But I'd suggest looking at chemical anchors for the lift vs. the typical wedge anchors just to seal holes and help further bond the two layers together.
