My friend has one, not sure they did anything! Not much room for baby to get into mischief! They did change the front seats to a rock & roll bench though so a car seat goes between driver and passenger and they can flip it over and put the baby's basket/travel cot on it. Not sure they've used it over winter though except as transport so not sure what'll happen now the little one is 12 months!
We have a T4 with a bench seat next to the drivers seat, we are going to replace the seat belt on the bench seat side nearest the door as it goes a bit slack sometimes, the middle seat only has a lap belt so would ideally like to replace it with a proper seatbelt so Bean can go in the middle for ease of getting in or out; but I think you need to pretty much replace the whole bench to be able to achieve this! May get a swivel base fitted to create more sitting space in the back. DC1 due early April so we will probably only use the van for day trips or when needing to take lots of baby and dog gear when visiting family. I don't think we'd use it for camping until next summer when baby is older.
We had a T5 VW and baby's carseat was strapped in the middle front seat (bench) between us when we travelled. Then there was just about enough room to squeeze the travel cot at the end of our rock n roll bed in the back. We didn't do any baby proofing, other than ensuring that he couldn't reach anything from his cot! You can get a special hammock that you set up on the front seat but we didn't end up doing it due to being worried it would get too cold in the front. We've sold it now as baby no 2 expected in a couple of weeks. I miss it!