Played this scenario yesterday evening. It looked interesting as the French force has its back to a river, with a single bridge across in the centre. The French player gains victory banners for units that cross the bridge and exit the board. The stronger British forces start some distance away. So the British need to move up quickly (not what I'd usually do) to stop the French just marching off the board. Of course, if the French stand and fight, the British could be in for a mauling.
A random draw saw me playing the French. My opponent, John, stated moving up the British while I adjusted the French positions. Skirmishing on the French right saw the British rifle unit damaged, so I hit it with cavalry and finished it off. Unfortunately, this left the cavalry under the muzzles of the British artillery and they didn't last long. Drawing the right cards (Grande Manoeuvre, Short Supply and Bayonet Charge) let me move away from the British forces and start taking units off the board. Cover was provided by my other cavalry and some light infantry, both of whom paid the price. It was a win for the French by 6 banners to 3.
Swapping sides, we tried again. As the French, John started pulling back immediately, but his retreat stalled as he ran out of the right cards. I was able to push up my light infantry on the British left flank and inflict some casualties - though I nearly lost the rifles. As I brought some of my right flank troops into the centre, John attacked my left with his cavalry, but some lucky shooting by the Portuguese light infantry killed one unit and chased off the other. The French won again (despite the British not losing a single unit), but the score was 6:4, giving me the aggregate win 10:9.
To follow up on that, both John and I found the scenario frustrating: the French need centre cards, the British need left and right flank cards. Both of us spent periods with useless cards in our hands. This works for the scenario, but was painful.
I'm not a fan of exit scenarios, but the solution to these kind of unbalanced scenarios (in a general sense) is to increase the exit requirement.
e.g., score a banner for every unit exiting after the first 2 units exit.
Glory is fleeting, but obscurity is forever.