I do like the idea of customizing the dimensions of a mouse to fit my big hand, but I also love my Logitech G5. Perfectly comfortable; good grip for sweaty hands; adjustable weight (I would like my next mouse made form solid steel and tungsten weights please), and I only occasionally use the extra buttons it has.
I have the Saitek Cyborg X joystick, and I love how comfortable it is, all the buttons, and adjustability.
Unfortunately, it's by far the worst joystick I've used. Great on paper, but pore in practice. Maybe if they built the same joystick, with just a significantly higher level of quality, it'd be perfect.
I also have some random Saitek controller from 10+ years ago, and I love it.