Everything except the Y key you can get with a Perixx Periboard 535. It uses mechanical Choc switches.

The closest thing I’ve seen to moving keys to the other hand is keyboards with two B keys, so you can type it with either hand. I haven’t seen that for the Y key.

You didn’t specify whether you want row-stagger or column-stagger. Given that you don’t want to change your typing habits, I’m guessing row-stagger is what you’ll prefer. Transitioning to column-stagger would throw out a lot of your muscle memory and require some time to adjust, especially if you’re used to non-standard fingering. Typing Y with the right hand would be a minor change in comparison.

The “half-swept” version of Sweep does that already: https://github.com/davidphilipbarr/Sweep/tree/main/Sweep half-swept

The easiest way to make the board flippable if to mount the controller upside-down on one side. Half-swept uses solder jumpers for all the pads of the controller footprint, which does basically the same thing as flipping the controller.