With prep time involved I can see this happening.
Blood lusted, and with the intention of beating their opponent.
The vary first they would do, would be to merge. Yes X-Man has gain the ability to merge with his alternate selfs.
What does I do? He gains physical aspects of his alternate self, plus knowledge and experience.
Best thing about it…is it works both ways. Both Cable and X-Man gain equal footing.
Since both have gain physical and mental aspects, both can proceed to use multi-versal telepathy and link their minds across their alternate selfs. Thus gain knowledge from all other Alternate Nate.
With that said, physical they can rearrange their physical body to a molecular level, and increase their strength and durability.
Now both have the strength to take planet wrecking shoots, and enough strength to shatter the moon in a single blow. Both make psi armors that farther increase their strength and durability. Enough to take exchange blows with the Hulk, and with stand shoots from Thanos. If you think it ends their, they can still put up, TK barriers enough to with stand blows from the M’Kran crystal guardians.
With everything said, I think I have given more then enough reasons why they would be able to handle and take blows from Thor or BRB.
Now its your turn (who ever you wants to challenge).
End Result
Cable and X-Man gain the X branded mark, and Deadpools Healing factor.
Cable and X-Man has gain knowledge and experience of one another, plus all the other alternate selfs.
Physically they augmented their strength and durability.
Armor made from Pisonic constructs
TK Barriers up.