Wasnt it
@California_Tanker who suggested that theres a case for Autoloader and 4 crew - (if not here then on his you tube account)
Something along the lines of - the 4th man can moniter APS / surveilance and help with maintenance yet the tank doesnt need the 4th to fight efectively and so 3 with auto loade if youve bodies either sick / injured or on holiday
Edited to add - he may also have argued it was potentially safer in that there wasnt an open door to the bustle (Abrahms) quite so often or for as long - but i wouldnt wabnt to put words in his mouth
TBH, I've been thinking along the same lines. I reckon you could have the crew in parallel. So Gunner and Commander in normal positions, but then have the Sys op guy behind the commander (possibly facing rearwards as a space saving measure). This dramatically cuts down on the amount of fighting compartment frontal cross section you need to armour, which is traditionally where one puts your most protection. As armour is one of the big expenses for weigh it would (theoretically) mean savings in weight.
The down side of such a set could mean a bigger turret ring than we normally have. However, as I have previously mentioned a four track tank could, if not avoid, then alleviate this issue.
Autoloader in the bustle, possibly spare ammo and other kit in the position to the other side of the gun. Again with careful placing of less critical systems in this location then you could absorb any penetrations to avoid an instant Mission kill from a penetration. If, for instance you placed ready rounds in the unmanned turret side. They'd need rams to load them into the autoloader. This would be at the front, and so knocked out first. Even if that, COAX and other secondary systems weren't sufficient then you'd get an ammo detonation that knocks out part of your ammo reserve. You'd still have the fighting rounds in the bustle part of the autoloader.
The only thing that worries me about this thinking, is concerns about overall weight, it feels like one is double spending the weight allowance. It'd be something you'd need to sit down with your FVRDE and do some calculations about...
Oh.
Bugger.
Come to think of it, there are tanks that sort of fit the description. With four man crews and autoloaders after a fashion. They have 'loading assists', which seem to be loading systems that get the round into position, and just require the loader to shove the round home (so about 2/3rds of a full blown autoloader). But these are modifications of conventional western MBT's.