This is what I came up with. It's the challenger that I used as the base. I added an insulated compartment to the bottom, moved the storage compartment to the back with the same zipper as the disc compartment but on the side, put a cushioned seat on top (with the smaller square being a cutout with a depressed cloth and rubber handle), and moved the putter pocket (preferably holds 2 putters) to either the left or right side. I'd also like to move the cupholders to the base (cooler compartment) and have another smaller access to the storage compartment on the side with the putter pocket.
My idea here is instead of adding a seat to a bag (like what most bags with seats I've seen do) add a bag to a seat, so I'd want a rigid (steel/titanium/nanocarbon etc.) frame that could support someone and probably something durable on the bottom of the bag like rubber pads.
This is a bag with the tournament player in mind or the player (like me) that likes to take long trips of disc golfing. That bottom portion could hold lots of cold water/food/other beverages and the back pocket (could be subdivided) can hold layers of clothes, towels, snacks, extra discs etc.