Hey friends,
First of all, thanks for all the advice a while ago. I don't think I expressed that enough.
A bit of an update: Thanks to the advice here I didn't go through with my plan. The gator attack happened, but I ran it using the battle rules (as if it was a 3 armored large gang) and it turned out pretty interesting.
We continued along (using a few other suggestions here, most notably the ammunition shortage, why didn't that occur to me sooner?) and last week we had our last game. For the climax we ended up doing something similar to what I had in mind for the gator attack.
Right before the battle I told the other players that once they hunkered down into their positions, if they wanted to move they had to cross off something from my mystery list (in addition to rolling as normal). Whenever they took any amount of damage, they could negate it by crossing off something from my list. If they every failed a roll during the battle, they had to cross off TWO things from my list.
They didn't know until they had reason to see it, but each line of this list had a good thing and a bad thing (or in two cases just a really good thing). Bad things included various NPCs from the enemy side, various NPCs that had recently betrayed them, and really good things that they enemies had. Good things included things like 1/3 of the combined gang (that was there three times of course), NPCs they really liked, and (my favorite) "your favorite limb." The really good things were an NPC child ward of the gunlugger and an unrequited love of the Maestro'd.
I think there were 10 or so lines altogether. My favorite moment was when it came down to the ward, the love, and your favorite limb/[npc turncoat] and the Maestro'd failed a roll on the last round of the battle. He took a long time before finally choosing to lose his arm and save the ward. He narrated saving the girl (I should note that the gunlugger and maestro'd characters sort of hated each other, so this was all the more heroic) from a grenade or something, but exploding his arm in the process. The game reflected the meta-game decision, it was pretty awesome.
After the game I asked if that list was ok, and the gunlugger and maestro'd really loved it. The chopper was less enthusiastic about it (he lost all but one of this 30ish strong gang), but he said he liked it too.
Anyway, sorry for that huge block of text, but I'm glad you talked me down from using this a while ago. It seemed to work really well as a closing to a game though (although very modified from what I had in my the first time).
Thanks again!