I have a traditional heating system, it puts out 70C hot water. I certainly cannot replace it by my HRV but it could be complementary. But I guess that the air volume handled is too low to work as a real heating system, usually that kind of systems move a lot of air to heat a whole house. Your suggestion to separate the heated flows is valid, though
I must see how this would change the whole design of the unit as the space is not that big down there.