I'm glad at least one person said it. I believe the whole reason that they try their hardest in the anime to keep his body safe is because without it he would be fucked. Sort of like an Akashic projection, if the base is destroyed the projection does not just continue on from where it was, it is recalled.
The response a proper fanboy would give.
If needed, Dr. M could just run off to the dark side of the universe to study, provided there is no time limit on said match I am sure even joe blow could learn how to influence the spirit world with basically godly powers after 2 million years of research. Because how is a swordsman with 0 'kido' (aka magical cheating) powers going to keep someone who is practically a god in place long enough to do anything. If you want to go further, on the assumption that Dr. M is immortal he could win without even fighting in the slightest ala Aizen arcs
Baraggan Louisenbairn who proved: "death by aging is something that the mind cannot fathom except for the fact that it is inevitable, even for Shinigami." Though honestly I see Barragan as most probably the strongest entity in the Bleach manga as far as raw power and defense goes.