I like this idea, I currently heat my home and garage with a hydronic source, and have no A/C. I could easily plumb in the chiller water into the existing heat exchanger in the forced air unit.
Well you would most likely experience higher electrical usage with a wall of pumps system. Alphas will be vast overkill for most single zones, going with a manifold and actuators would be cheaper as well. How many zones are you planning for? A manifold mixing station might be the way to go...