I'm looking for a reclaimed 1930's panelled front door (three tall below,
glazed above), and the one we've chosen is unfortunately cut for hinges and
locks on the wrong sides.

It has a mortis lock (with both ordinary bolt and deadbolt, so quite a chunk
removed from the door), and a Yale-style rim lock. The mortis is mounted at
the same level as the cross beam below the glass.

How compromised would the strength of such a door be if I were to slot a
piece of wood into where the mortis lock was (screwed in place maybe?), fill
the old rim lock hole and hinge slots, and hang on the side where the old
locks were? I was planning on having just a good rim lock on the new side
(e.g. Yale XBS2).

Or should I keep looking until I find a door hung the right way (which never
seems to be the case with doors which will fit our frame!).

Thanks,

Ben