Brakes:
Watch out for compatibility issues with the pull rate on the levers and calipers.
Old school levers and v-brakes can be a problem.
New levers and old cantilevers should be ok, but always check the action.
Shifters:
What are you planning for shifters?
Brifters, down tube clamp on style or perhaps a Suntour command shifter?
Mixing brands and vintages( of index type systems) can be a problem.
Friction stuff generally works with mixed brands.
This may be the more difficult aspect of your project.
Good luck.
rusty