Use existing dual extruders on the market?

I’m hovering over my shopping cart to order my TAZ 4. But I need dual extrusion–triple would be awesome! I’ve looked at the kit, and sourcing the hardware alone seems like it’ll be a pain. I can’t find the springs and motors in stock anywhere. I know that the official one will supposedly be released soon, but I need this for work and it’s rather urgent. They’ve been saying it’s “almost” out for months and months.

How hard would it be to implement an existing dual extruder, that’s currently available? Cost isn’t really a big deal. Like for example one of these:

Man, I would LOVE to get this quad extruder setup, but I think the electronics will only handle 3, is that correct? What would it take to get one of these working (even if it’s just 3 of the hotends)?