Yeah the dump area idea is probably less wasteful. You can mix extruder types sure as long as each is calibrated correctly.
There's a lot to commend mixing hotends like diamond such as wipe and prime-free colour printing, Ian is resident expert there. Switching is just easier in some ways, trickier in others.
To be fair I got dual extrusion setup and working then gave up on it as my flying bracket was making my machine heavy, slow and less accurate. Dual/triple cable driven extruders would probably be the optimum.