Okay, looks simple from a user point of view. To make it shareable for everyone to edit, is it just a tick box when you upload it?
If so, this will make Binder Fred happy over in Dawn of Defiance. He likes to move his own token around.
Though if a player makes a mistake, it might be hard to catch or fix it without a history. That's the one advantage by having it completely under GM control. Honestly, with only three players, an updated grid every round would be fine with me, leaving the GM with full control.
I am easy going, just let me know. I personally like picture tokens, much better than looking at my letter on the grid.