I don’t think it’s going to be much harder. The JLF and JLF clones have five prongs that connect the stick PCB to the main PCB.
If you want, just remove the stick PCB and put 4 microswitches there instead. Then wire the microswitches to the main PCB directly. That way you can solder the grounds on three of the directions together and have the fourth switch have its own ground. If something goes wrong later, you can always put back the JLF clone’s original PCB and microswitches.
You’ll end up with a set-up similar to Hori stock joysticks, which have no stick PCB and just have four microswitches by themselves.
Similarly, you can just scrape some contacts on your JLF clone PCB and make it non-common ground. Then you can wire it the way I described it above. There’s a tutorial somewhere on SRK.