There are already unmanned turrets, so why not. The question is, in what roles this would be actually useful?
> If you have no crew at all you can devote more space to machinery and ammo, and you could have the crew in a different vehicle that can control a whole battery of them, with 4 (or how many SPGs you have in a battery) soldiers dedicated to controlling a single SPG each (mostly driving for them from position to position)
>Of all the vehicles you could turn into a UGV, you chose the one and only that gets to engage the enemy from a safe distance and has no reason to be remotely controlled in the first place?
If it was engaging from safe distance, it could be replaced with a cheaper towed
Speaking of which, if you need only a more expendable mobile battery without local human spotters and decision makers, SPG is superfluous. It can be reduced to unmanned towed
The same unmanned turret carried on a light frame with wheels and hydraulic jacks. If it’s lowered onto the ground for shooting (much like many railway guns work), there’s no no need for unlimbering or having a heavy platform capable of taking full recoil every time. Anything not really needed in the turret goes into cart, if not really needed there either, into the tractor. An unmanned artillery tractor can be made quite flat, too.
Also, since the turret must be both lean and self-contained, the gun is modular
now, so for a long-term position the turret itself can be either trivially detached and left there much like manned towed guns, or even better: mounted on field fortifications for easier supply and wired control.