I will support a call for caution in changing the spotting / call for fire rules.
I don't know what was the Soviet system, I'm not sure how it worked in US army in WW2. So to illustrate the complexity of the issue I will use the example of Polish Army pre-war and during 1939 Campaign.
Normally artillery which was supporting infantry was developing fire-plan and deplyed forward artillery observers to correct fire. That was the normal way of doing business.
At the same time every officer, starting from platoon leader and company commander were trained in artillery system to be able to call for arty fire. And that what was happening during the campaign. When the artillery observers couldn't do their business (killed, wounded, on the move etc.) it was up to commander to call for fire. And they did.
So giving all authority only to the arty observers (or whatever you call them) is a bit decreasing the training for unit commanders.
The only solution I would think of, if the Designers want to make changes, is that arty called for by arty observers has 100% of being properly (I mean accurately) provided, while arty called for by units would have - lets say 10% possibility of being drifted one hex or so.
But that creates another problem, how to judge every specific commander of platoon? That would arise another problem how to compare German, American, British, Polish, Soviet, Dutch etc officer training? How to compare their communications systems?
That would be a good material for PhD dissertation
Taking above into consideration, and improvements already being made, I would say
don't fix if it's not broken.
Just my thoughts
Slawek