I get wanting to have a near playoff ready roster day 1, but IMO there's more value in giving Mo runway at DH vs blocking him with someone who at most is going to be marginally better. If at the TDL he has a 115 wRC+, great, you don't need a LH hitting DH. If he struggles, make a move for a platoon bat (they're a dime a dozen) and send Mo down to work on the what they've learned about him facing big league pitching.