It sounds like an Ultralight is what you want… I paddle class 1+ in the Ultralight and sometimes carry my wife with me on lakes. If you dig through my old YouTube videos you can see me doing these things in earlier versions of what became the Ultralight. Just four days ago a customer who built an Ultralight emailed:
“By the way last weekend I took it through a very dicey little river between two lakes where it rubbed against a bunch of sticks on both sides from a destroyed beaver dam and it held up great. Impressive.” He also sent pictures of himself paddling through ice in the arctic.
If you’re not convinced, I recommend ordering a fabric sample pack so you can test the fabrics yourself.
Regarding the fabric weights, you’re talking about substituting fabrics with TPU on one side in place of fabrics that have TPU on both sides, which could be done but it would leave exposed fabric on the bottom of the packraft, which would soak up water and then be heavier than the double coated fabric and it would be less resistant to abrasion.