What extra resistors? Analog cables are nearly always manufactured with 75 Ohm coax and it works fine. Should not be a problem at all. I've seen it done for people who have separate DVD-A and SACD players.
I don't see what the problem is? Just run the HD-A1 via digital and leave the DVD-A player on the m/c input. Component video switchers can be used to switch audio also.