I read martial arts + shield was pretty good for holding attackers at a door.

Not so much a "best combo" but an "ironic result" I got from giving one of my colonists his first superpower. The guy got the "Redundant Stomach" superpower (which makes it so he doesn't need to eat) and the "Hypermetabolism" weakness (doubles hunger rate) from the same operation which means that his weakness got cancelled out by his superpower.

Invisibility is exceedingly strong on its own. Pawns don't get targeted, can attack, can block a door.

I was planning on making a half warg half man pawn using pawnmorpher and tryna get him metamorphosis + regen + regen limbs + speed burst + plasteel claws.

Then adding some animal power armor for his warg metamorphosis from the animal clothes and armor mods.

Not sure if it will function as I imagine but would be cool thematically if it does all mesh well together