More Exit Options for Passenger Vans

We run a Photo Tour company here on Kauai and we use 4 Ford Van 2 are Econoline 350's and 2 are the Econoline 150's. The biggest problem we have are getting people in and out of the 350's back seats! I wish there was a way to add a door for the back seats. Can they put a door on the same side as the existing doors or maybe one on the other side for the last bench seat. We won't even get the 15 passenger because of the difficulty of getting in and out. Please if there is a way to make it better I am sure Tour companies and families all over the world would appreciate it!