Based on our experience with our 26' Tioga RV, IMO, the design of the 2nd row seats should be a higher priority than given in most camper van designs. I spent a lot of time in our RV's (uncomfortable) dinette seats. The 2nd row also comes into play if you want to take more than just 1 friend on your adventures! I bought some sweet 2nd row leather seats off Craigslist and designed a lot of the rest of the van around them.
Because these seats come from a minivan, when anchored properly to the van's frame and supplied with proper seat belts, they should be a lot safer than a typical RV sleeper sofa with lap belts. They are very comfortable - they recline and have dual armrests. My current design allows the seats to be easily changed from being mounted longways to mounted across as I believe that passengers generally prefer to be facing forward.
I really liked the the black leather on the minivan seats. The original cloth front seats were not great and they stained easily. There is a company here that does amazing aftermarket leather seats. I had them recover the front seats to match the 3rd row. There is a before and after pic below.
I bought 4 point racing seatbelts. I discovered that I could get away with using 3 mounting points - 2 on the sides and 1 behind the seat (see pics). For each seatbelt, I used 2 of the biggest bed bolts I could find (see pics) and one of the original seatbelt mounting points for the 3 mounts. My 2 bed bolt mounting points probably wouldn't pass the 4000 pound NHTSA requirement, but I'm confident they are much, much stronger than what was in the rear seats of my Tioga RV. I mounted the row to the floor of the van with 2" structural aluminum angle and more bed bolts and bolts to attach the seats to the aluminum angle (see pics). With 4 x 2,600 pound attachments points each, the seat attachments are probably good for 4,000 pounds.
I have more tips for anybody trying to replicate this - just let me know and I'll write more and/or answer questions. The most important tip regarding the use of bed bolts is to watch the clearance on the gas tank carefully. As supplied, the bed bolts were clear of the tank, but just barely. Eventually, I decided that the bed bolts had to be cut shorter to provide more clearance. My tip is to choose the final length of the bed bolts before you do the final install and replace the gas tank!