I'm leaning more away from military vehicles myself. It is a lot easier to find spare parts for vehicles that are based on commercial designs then military designs.
The Terradyne Gurkha series that is based on the Ford F550 platform. The 3 different models can be modified for MP use, to provide different teams a vehicle on a common platform.
LAPV or RPV - Recon, MARS, etc
MPV - CP, Ambulance, Specialty Team, etc
http://www.terradyneinc.com/index.html
https://www.youtube.com/watch?v=oJ-Jiz3YVGI&t=87