It seems like the mtb crankset would be wider than the road crankset to get the 50mm chainline so adding spacers as needed should make the crankset fit. Then the issue becomes when you space the drive side to clear the chainstay will your FD how enough throw to reach the big ring. It probably depends on the chainstay geometry, chain ring size, etc. I'd guess it will work but I'm not the one paying for the parts.