Anyway, as an attempt to get this back on topic...

Looking at Used Car Lot and Arsenal, you could try making a sort of mobile fortress using an 18 wheeler with a trailer as a sort of base template, maybe the Zuggsmaschine in Arsenal (pg 111), or the Trailblazer in Used Car Lot (pg 23). You could put concealed gun ports all over the trailer and armor the outside, and possibly place a remote controlled turret or two on top, controlled by a second rigger in the cab.
You could go the Go-Ganger route and just tell them to pick out a motorcycle that they would like to have, with two custom mods each under 10,000 nuyen each.
Have you considered a boat instead? A yacht could handle a large party, if your players somehow ponied up the cash. Failing that, a pair of utility watercraft...
Failing that, you could try to cut down on your party to two separate teams. I hate to say this, but are you sure about GMing a ten to twelve person team? It would seem that combat would get bogged down awful quick which would bore the people who were hoping for a roleplay-over-rollplay experience, and that the chances to focus on story or details would be problematic with the opposite group if they just want to kill stuff and get loot.
Regardless, there you go. Hope this game works out for you!