My preference would be to run scouting operations either as a skirmish game by itself, or fold it into a bunch of modifiers for detecting hidden troops in a larger scale game.
If in a larger game, if you want to put scouting models on the table, you can use them as triggers for a modifier within a specific distance. Possibly use a random events table to determine the fate of scouting parties.
More generally, it is connected to the problem on how to represent/detect/move hidden troops on the gaming table, and how you can turn that into sensible gaming mechanics. Many approaches for this have been suggested over the years, but it remains a tough problem.
Even more difficult, is to widen the issue towards gathering information: state of terrain, weather, supplies, etc.
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