If you check the published army lists, units with the scout ability tend to be pretty rare. Most lists have none, and those that have them tend to be limited to a single unit of skirmishing infantry or light cavalry.
As for trying to represent scouts (or anything else) with single model units on the tabletop, I would recommend not trying that as it could get rather fiddly, and the game is likely not designed with such units in mind. Not to mention that the game is supposed to represent the part of action when the armies are closing in and getting ready for some serious action, by which time any tiny patrols would probably have fallen back and formed into larger units.
If you are looking for a game where various advance parties play a more serious role, you could try adjusting the escalating engagement scenario, where each side has in the beginning just a skirmishing party on the table and other units arrive as reinforcements. Or maybe a mini-campaign where you first play a couple of small games (say 500-750 pts) where cavalry and light infantry forces clash with each other for information, forage etc. with the results of these games then providing some advantages in the actual final big battle between the two sides.
As for how the Scouts and Hidden Ambush special rules work together, the rules currently are a bit vague whether the ambush markers count as enemy units for the purpose of deploying scouts. Easiest would be to rule that they count – though this might then limit the deployment options for the scouts quite a lot (then again, for skirmish infantry Scouts is a 1 pt upgrade per model, so should not expect too much from them).
Of course it would be possible to write some house rules for the Scouts vs. Hidden Ambush case. One option would be to rule that the hidden markers do not limit deployment – but if scouts deploy so that they reveal a hidden unit, they then need to fall back certain distance towards they deployment zone.