Sorry but I do not know much about these trucks, but I do know that they are not popular outside of France.
The UK RAF did use some Renault trucks for something or other, but not the ones that you mention. The MOD disposal agent has been selling them for a while. They've got a lot going for them and I think they'd make a great world travel rig.
I need the double cab for all of my offspring or else id keep my MB 917. And it seems like all the other double cab firetrucks are huge and seat 9 people. Kind of a too small or too big kind of thing.
The British Daf 4x4 trucks have a pretty big cab. They are designed as a sleeper cab but people have adapted them to fit kids seats in the back. I'm not sure how comfortable it would be, but it's possible. They use a Cummins 5.9 engine but I believe that some other drivetrain components are one-offs for this truck and can be difficult to get parts for.
The DAF is a similar size to the Steyr 12M18 and the FMTV family of truck cab. Bigger than a standard cab but still limited to side facing jump style or kid car seats.
It is interesting how they jump up to the much larger size after these. Those bigger cab really do cater to the firefighter vehicle.
My thought was to swap the engine for a 5.9 Cummins. But yes getting parts for that engine is nearly impossible, or so it seems. Its a similar engine MAC was running in the '80.