[folivier]

It would seem as long as a different motor will fit and has similar hp and rpms then the only other factor is making the blower fit. I don't remember but do the dometic units have a single or double blower? Blowers should be available to fit a new motor shouldn't they?
Another thought is to search on yachting sites since the a/c units they use are similar sizes with the major difference being a water cooled heat exchanger. They may have a blower motor with similar sizes.