I have trouble with leg cramping, and often take my right shoe off to get a bit more extension in my ankle. So I know what your after. I've had the seat out a bunch for the stereo so I've seen that up close too.
you could put a stack of washers under the front mounts and tip the pan back, but you would also be raising the pan, which I found to be a bus driver throne the first few days in the car, I don't notice it much now, guess you can get used to anything. it would also increase the bending forces on those bolts in a collision. much more than a 1/2 inch stack could get into a gray zone
the better way to do it would be to lower the rear mounts. but that would take two very nicely made brackets. not for the faint of heart.
you will need to be able to design and weld