Try using hierarchical sheet symbols? Then you can instantiate repeated sheets.
Have fun with the net errors on that project; you can probably (and probably should..) turn off basically everything (errors, netlist compile, PCB transfer..) in such a project so it does exactly what it's supposed to do and nothing else.
Not something I've done / had to do, but a neat idea. One rub: if you have assembly variants in the main project, those are project-specific settings and won't follow the sheets (of course).
Tim