Technically it is possible, Altea has this capability. But officially OW does not support through check-in on separate tickets (CX could be the only exception), so rejection may happen.
OK cool, does MH use Altea too?
As for separate tickets, I've never had a problem
checking through on MH connecting to other OW on separate tickets. And it's also definitely a
published benefit on QR - there are whole
threads discussing it...