Dianno wouldn't have responded positively to such a demand. He's on record saying he didn't get into rock and roll to have a schedule and have to get up early in the morning. When the band started touring internationally and had obligations and commitments he really wasn't up to it because he really was a punk.I would like to think if he were given an ultimatum to clean up or get out it might have gone different for him.
But after hearing Steve Harris say Dickenson was the singer they always wanted I wonder if the replacement was inevitable?
Anyway, I somehow forgot to mention Strangers in the Night by UFO.
The versions of Mother Mary and Rock Bottom on that double album are far better than studio.
Most 70s bands of any worth had really good or even great live albums.