The Lonious Monk
Celestial Souljah
I'm going to assume that any version of events that included cutting his arm or hand off would have ended up with someone else getting the gauntlet and doing even worse damage than Thanos.
Best case scenario was letting him go through with the snap.
The writers actually addressed that a little. They said that Thanos is powerful even without the Gauntlet and that there was no guarantee that just because the heroes got it off that they would have been able to keep it away from Thanos.