Put a fiberglass shell on the pickup and that will provide a secure place to store gear and you can add rain gutter adapters so that a Thule or Yakima roof rack can be mounted. I have this with my truck and transport two Hobie kayaks on the roof rack and two bicycles inside the bed of the truck. I could not begin to do this with a 5th wheel trailer.
I tried an inflatable boat and a Porta-bote and was thinking about inflatable kayaks but for our type of travel the Hobie kayaks are much better and more fun. We use Thule hullavators to lower the kayaks down to chest level and this makes it easier to manage their weight.