Double sided boards as we all know can be a bit of a pain, the biggest problem is getting that precise alignment between sides correct so that when you drill in the center of your pad on one side, it comes out in the center of the pad on the other (and not, as is not uncommon, breaking out, and probably messing up the trace, or a trace nearby...). Especially if your only able to expose/imprint artwork one side at a time.
Even more frustrating when one side comes out perfect in part of the process (eg, developing) and the other side is too flawed to be useful, meaning you get to start from scratch again.
Of course, it does double the drilling, but that's the easy bit really.
This is also of course more or less how multi layer PCBs are made by fabricators, a stackup of already prepared pcb layers and resin impregnated sheets.
Single sided laminate at 0.8mm thick (and you can get down to 0.5mm) is available out of China for cheap.
Eg:
Has anybody done this... am I reinventing a triangular wheel here, is it doomed to failure? Suggestions on suitable adhesive... maybe just spray on contact adhesive might work, it's a pretty big flat contact area.