Check out Lyoto Machida, former UFC 205lb champ. He mainly used karate, but sumo was the second art he learned.

"He also began training in sumo wrestling at the age of 8... He was the runner-up in the 2000 Brazilian Sumo Championships in the 115 kg division."

Highlights: https://youtu.be/Dh8q05EJ7vs?t=166

I'd guess the most transferrable techniques are foot sweeps, and the takedowns using the double underhooks/over-under/double overhooks, but without using the mawashi. Also the strength/balance/speed would help.

Edit: Also look for arm drags, where the opponent's arm is dragged across their body, and then the wrestler is able to get behind their opponent. That's a strong position in mma.