The history of the Border rivers has everything a skirmish player can want. Pick pretty much any scenario and you can use it for the Reivers.
Raids are obviously the most common. But the raiders were sometimes pursued by the 'Hot Trod' which was a semi legal reclamation raid (as long as someone was carrying a burning piece of peat on a spear at the front). however some hot trods were then ambushed by the raiders, with the raid just being the bait to lure the others in. You have the march wardens or a family in their pay having to arrest someone for trial or the family rescuing some such person. You have spies/messengers trying to get across the border with information for the scottish or english regent.
Just reading some of the exploits of Kinmont Willie gives an idea:
https://en.wikipedia.org/wiki/Kinmont_Willie_ArmstrongThe two ospreys about the border rivers are fairly decent, but George McDonald's Steel Bonnets is the best source. Also Alistair Moffat's book 'The Borders' has a decent shorter chapter in it about the reverse, that's more easily digested than Steel Bonnets.