I have reviewed a lot of YJs and their stretches to get an idea when I do mine. A lot went with the fuel cell route behind the rear seat. Then they removed the rear seat.
Here's my thought and what I'm planning. Keeping the relative distance between diff/cover and the stock YJ gas tank. If you move the diff back, move the gas tank back. Going to be building and strengthening a rear cross member or extending the frame for the shackle, so why not keep the relationship nearly the same. They may be a design where it won't quite work but if it was a thought and a possibility in the design and layout, not too hard to accommodate.
Like in the pic of the rear side
that rear crossmember/bumper could be changed to carry the lower skid plate of the stock tank and a crossmember up front to carry the front. Stock tanks are sandwiched between pair of top straps and the skid.
All that can change as well. Take straps top and bottom of the tank to secure it hanging from frame points, and like the flat belly plate, a separate skid can protect it. Then, possibly, an access door can be placed in the floor behind the rear seat to access the fuel pump itself limiting the need to drop the tank for an issue.
Then add a TJ fill tube layout.
That tow hitch point is really too high to be used to tow a trailer (other than custom). Most are 18" high. Reconfigure recovery point(s) more off the frame rails.