I've been working on a scenario book supplement for Fistful of Lead centering on the Mexican Revolution. Part of that is making sure all the scenarios actually work.
We've done the Battle of Casas Grande, and it worked really well. Following the timeline of the war, we tried the second one, the Battle of Tijuana.
The game involved a rebel Maderista force attacking the Federal troops inside Tijuana. We just centered on a small section of the town, with the railroad defining the US border.
The special rules this time were fires burning around the town. Models could light or fight these fires and any model caught in a burning building at the end of the turn was forced to roll on the Wound chart.
There was also a turn limit and barricade rules. All in all, it felt balanced. The turn limit forced the attackers to move forward, rather than sit back and pound the out numbered defenders. The result followed history, with the attackers (including some American Foreign Legion troops) taking the city just in time.