I'm only an amateur physicist, but I don't think there is any more stress placed on the jacks as long as the feet have leveling blocks custom cut for the pitch of your driveway. If you don't use leveling blocks (wedges?), it would put more stress on the feet of the jacks since only part of the round foot will be contacting the ground.
I have unloaded our camper once on our sloped driveway, but I would estimate the slope as a 2"-3" difference front to back, so a lot less than yours.
I don't know how you plan on using the truck ramps in a manner that you will be able to drive off of them safely from under the camper. I normally unload our camper on a gravel section of our driveway, and if I don't rake out any moderate irregularities first, it makes it difficult because there is so little clearance between my rear fenders and the jacks (less than an inch on either side). I don't have bracket extensions, but they would alleviate the problem. I just can't see how you would have the truck on ramps, disconnect the camper, then drive off the ramps and out of the camper at the same time without that major movement of the truck bed being a problem. I also don't understand why you need them. The jacks will level the camper. Park truck, disconnect, lower jacks proportionally to level the camper while the truck is under it, then drive out slowly. I would probably want some decent clearance between the bottom of the camper and the truck bed because the rear of the bed behind the rear axle might not just go down parallel with the pitch of the driveway, and it might end up rubbing the rear of the camper as you pull forward (assuming truck nose is pointed down hill).
I think one issue you might have is running out of jack. Not sure how tall your rig is, but my stock Ram 2500 is tall enough that I get close to running out of jack on level ground. So if your front jacks are needing to be 8' higher than the rears, you might not have enough.
My diagnosis: Based on minimal information, it's theoretically possible to do it, but if you haven't loaded/unloaded a camper multiple times on optimal level ground, I wouldn't recommend it. There is a lot that can go wrong and you really need to understand all the variables in the process before coming up with a system to safely do it on the slope. Having to use special feet on the jacks adds another variable that you need to think about before doing. I wouldn't want the wedges shooting out from under the jacks because there isn't enough friction to hold them in place. And when you put feet on your jacks, then you have to make sure your rear wheels won't roll over them. If I were to put blocks under my jacks, they would have to be no larger than the stock jack feet because my rear tires actually kiss the front jack feet when I load/unload.
