I can think of some ways to do that, but it's going to require at least Dynamic Lighting (Plus or Pro subscription) to do it, and probably some API scripts (Pro subscriber perk) to do it well. The problem you'll run into with a Free account is that your only option for restricting visibility will be Fog of War, which is an all-or-nothing option for players--anything revealed will be visible to all players. With just Dynamic Lighting, you could give tokens vision but no light on their own, then drop in lights to reveal areas as needed. You might need to box regions in DL lines to prevent seeing "distant fires". With the API, you could lock tokens in a location (mostly), or further automate the above in various ways.