You would be surprised at how many in this market prefer a professional shade to the pad hat.
I'm not sure about your statement saying that my contraption would render the tablet useless. The tablet slides in and out. It is one bolt to release and collapses down very nicely. The one for the mini can be mounted to the stock DJI phantom transmitter tray and weighs a little over 8 ounces. While the one for the iPad Air and the iPad Pro 9.7 can fit into the tray as well without the need for our mount and it weighs right around 13 ounces.
I confess I am intrigued by your description.

My Mini 4 stays
permanently in a slimline case that fits it like a tight glove, making it very difficult to remove. Will your "contraption" (for want of a better word---no aspersions intended) allow a Mini 4, already inside a slimline case, to still slide in and out of it, or will it only fit a Mini 4
without any case?
If a Mini 4 inside a slimline case can still be slid in and out, I might be interested in trying one for myself. I use the Khömö Slimline Mini 4 case from khomoaccessories.com which I purchased from Amazon here:
https://www.amazon.com/gp/product/B014RK8KQY
With the 5 ounce Khömö slimline case on it, my 10 ounce Mini 4 already weighs 15 ounces total, so adding "a little over 8 ounces" will add over 55%
more weight total, while the
PadHat weighs only 1.6 ounces, or 11% more weight. Huge difference! My main reason for rejecting the 9.7" iPad Pro, which already weighs 15.6 ounces naked, was that the same Khömö case for it added 6.8 ounces to the weight, for a total of 22.4 ounces. Adding 13
more ounces to that 22.4 ounces for your "contraption", would really require wearing a transmitter tray, as now we are up to 36 ounces or 2.25 pounds
just for the 9.7" iPad Pro with a shade! 15 ounces total is the comfortable limit for holding any iPad in my hand and typing on it. Mini 4 in the slimline case fits this bill, as does the iPadPro with
no protective case. 15-17 ounces in the transmitter tray, including the PadHat, is not unwieldy nor too heavy. I use a naked iPad
Air 2 in the tray for all my P3P's, and the Mini 4 in the slimline case for my P4. They both weigh the same. The fold-up cardboard 9.7" sunshades only weigh 8 ounces, but they also make the transmitter unwieldy for me. A black cloth over your head and the tablet, like early photographers used, to focus and the old view cameras, is really the
best tablet sunshade, but attracts too much attention, and invites muggers!

A golf umbrella over the shoulder is another cheap solution.