A couple of points. I own a PT Cruiser convertible, and almost bought the Combi Zues Turn because of how easy it would have been to get my son in and out of the car. My only issue was that it only went to 20 lbs RF and the only to 40 lbs FF. Combi has said they were going to improve those numbers, but I've not heard that it has happened yet. That said... In your situation, and money not being an issue, that seat may be a perfect fit for you, provided you can use the turn mechanism. Try it out. Design wise, that seat is tres cool. Damned stupid weight limits though... Grumble grumble grumble. Mutiny mutiny mutiny!
The Graco seats are actually quite nice. Well constructed and well made. As a company they are very proactive when it comes to fixing issues with their products. I like them a lot. One thing to remember about Graco is that they have a lot of different trim levels. You can get the same seat with varying levels of padding and EPS foam. The nicer seats cost more. It's a pretty simple formula.
As for a tool... How are you at using the heel of your palm? My idea is to sort of create another thumb there. Not in a Weird Science mad doctor sort of way, but with a velcro strap similar to the spoooooon contraption shown earlier. But instead of a spoon, you want to attach an appropriately sized and shaped drawer pull from the hardware store. Go to a local Lowes or Home Depot and look at all the drawer knobs for kitchen cabinets. Find one that is shaped correctly and then screw that onto some heavy duty webbing material or fingerless motorcycle glove. I'm thinking the fingerless glove would give you the most support. You can get them with a lot of reinforcement in the palm area, as they are made to keep your hands from turning into a burger substitute in a motorcycle accident. With that knob mounted, you should be able to just press down with the heel of your palm and operate the buttons. Now if this works like I think it will, then patent it, make a ton of money, and then take my family and me on regular luxury vacations all over the world. Scotland would be a good start, as I collect Single Malts!
Lastly, welcome to the board! I need some more testosteronaly charged snarky humour to add to my own here. Welcome to the dark side. We have cookies..... :evil grin: