Until now, every vehicle I've driven in my adult life has been without TPMS sensors, and I prefer it that way. Having an automotive fabrication background, I can understand the dilemma these engineers face with the NV200. They don't know if you're using your van at max. payload, unloaded, or somewhere in between. So, for liability reasons, they'll set the TPM sensor parameters as if you're hauling at, or near max. payload. I haul a 230# dirtbike and 70# of gear, so I'm going to wear out the centers of any tire I run on the rear if keeping the required pressure they've set. The factory tires are junk, I knew that from day 1. That's usually how OEM tires are and whatever. However, once I put a nice set of tires on, I want to run whatever pressure I want. Having that said, I am NOT claiming that I will perform this modification and I'm certainly am NOT TELLING ANYONE ELSE to do so either. This is simply info that you can use if you so choose. 
The NV does not have a smart enough system to know where each sensor is located (for example, some vehicles will tell you actual location of the tire that is low on pressure). Without getting too specific, one could take the spare tire, remove the tire from the wheel, and drill the needed holes to install all 4 sensors in the wheel. Re-mount the tire and inflate between the 44 and 48 PSI. Now, is your average tire shop gonna re-mount that tire on your newly modded wheel with multiple TPMS valve stems? Probably not, just sayin'...
The NV does not have a smart enough system to know where each sensor is located (for example, some vehicles will tell you actual location of the tire that is low on pressure). Without getting too specific, one could take the spare tire, remove the tire from the wheel, and drill the needed holes to install all 4 sensors in the wheel. Re-mount the tire and inflate between the 44 and 48 PSI. Now, is your average tire shop gonna re-mount that tire on your newly modded wheel with multiple TPMS valve stems? Probably not, just sayin'...