Use a square board. Place three cairns, statues or similar line-of-sight blocking objects along the centre-line - one in the centre and two on each side equidistant between the centre and the edge. These hold the treasure.
Set up terrain in any way you wish, but it must not be possible to cross from one side of the board to the other in a singe move. In addition it must not be possible for either player to reach a cairn from their base edge in a single move.
Here's the terrain we used:
The cairns are marked with orange counters, which represents the treasure they contain. There is one item of treasure per cairn. As you can see, the one can only be approached by skirting some ruins, one is on a two-level hill (we dropped it to a single level in the second game) and one is on the middle of a wood, entering or leaving which counts as a change in terrain.
A figure in base contact with a cairn, and not in melee, may use an action or a reaction to search it. They roll 4D6 - if any of them score a '6' the they have recovered the treasure. If two sides search as part of the same initiative - via an action and a reaction - they both roll 4D6. The side which score the most sixes finds the treasure first. If they score the same neither finds it.
Any figure can carry treasure. If they are killed then it is placed on the board where they fell and another figure may spend an action or reaction to pick it up. A figure may also spend an action or reaction to take an item of treasure off a friendly figure they are in base contact with, so long as nether is in melee.
If a figure reaches their friendly baseline then they may spend an action or reaction to 'bank' it. It now belongs to your side.
The game runs for an agreed number of turns. We played at least 12, but with a random game end after that, but you could fix it a 15.
A side wins if:
- They get two items of treasure off the board, regardless of losses.
- The other side has more dead figures than live ones at any point (as per the normal rules)
- If, at the end of the game, they have killed more enemy figures than they themselves have lost. Treasure which has been banked counts as two enemy figures killed for these purposes.
Killing the enemy warband is, of course, a viable strategy, but if they concentrate on treasure hunting before you inflict sufficient losses they can win that way. The third victory condition covers a game which times out, and rewards a player who has concentrated o collecting treasure in an otherwise even fight.
I don't know how badly Flyers or Cavalry would break this scenario, unless you set some specific terrain restrictions. But it worked fine with the warbands we used.