You can already have multiple mapped keys, with the same trigger/hotkey.

Ideally, one would start enabled, which is the default.
And the other would have the box checked to not load by default.

Then you have a two step toggle key.
That enables one and disables the other, on step 1.
And does the reverse on step 2.

You could load/unload entire Keymaps if you wanted, same principle.
I've seen the guide on using any key as a modifier.
It is essentially a two-step (execute on press or release) mapped key.
When you press the button/key, it unloads an entire Keymap and loads another.
And on release does the reverse.
So while the key/button is held, your alternative mapped keys (with the same hotkeys) run instead of the normal ones.