You can go big with a hard side TC that has the floor starting above the bed rails of the truck. This makes getting in and out of bed easy plus has a north/south bed. It will mean upgrading the truck to a DRW to handle that size and weight, but you do have options if you want to stay with a truck camper.
We went from a toy hauler to a truck camper because I wanted more garage space and did not want a bigger foot print. By putting the all the living quarters on the truck, I only tow the garage and am close to what my old length used to be yet have have a 20' dedicated garage. Quality toy haulers are heavy - I would stay with a tag hitch on your SRW because a fifth wheel pin weight will be 20-25 percent of the GTWR and may be pushing your limits. Since you have a short bed, you will also need to watch how much nose extends beyond the pin and possibly have to by a more expensive slider hitch. My 22' tag toy hauler was 7500 lbs dry and pushing 1200 lbs of tongue weight when I had it loaded to 11,500 lbs. Many guys see north of 1500 lbs tongue weight on tag TH's, so make sure your receiver is up to the task.