If you have a number of key combos you normally use, you just put that in a layer. You could make Mod2 + Home row = shift + cmd + F-keys, Mod3 + Home row = F-keys, Mod4 + Home row = cmd + F-keys, and so on. It would require some work to program the kb and adapt your workflow, but you will thank not having to do those contortions. IMO, a control flow that requires a lot of shortcuts that involve key combos like shift + cmd + F-keys is an ergonomic nightmare, don't adapt your hardware to that.