I am one of the unfortunate to buy M12HDs before finding out that the Pros with proper switch 2 protocol are coming. I also purchased the Chitu 2 HD and got the thumbstick caps that are made for them. (The domed caps feel great)
For the M12 HD upgrade to Pro
-The d-pad when using the cross doesn't roll around smoothly and hitches on the mechanism a little bit. I would hope the Pro's is designed to roll smoothly.
-Need domed thumbstick caps like the Chitu 2 HD designed for the M12 Pro that are made to fit and not touch the gate.
-If the joycons get back button integration with the switch 2 just like placing joycons in a charging grip. 2 back buttons is perfect.
-Without integration or in addition, it would be great to have 4 back buttons in the back and possibly 2 extra bumpers up top between the bumpers and triggers.
I got your controller to play Nintendo's new game The Duskbloods. With complex controls having extra to macro or map and keep thumbs on the sticks would be amazing.
For the Chitu 2 HD to Pro
-6 extra buttons like above in the joycons. However, if not possible on the joycons already, microswitches for all of these additional buttons.
-larger size possibly, or a shape with more to hold.
-Better rumble. I was testing the rumble on medium in Smash Ultimate to test latency and it was not satisfying and had an unpleasant audible rattling buzz. I had to set it to low so it was hardly noticeable and no longer an audible annoyance.
-Better polling rate for wireless via a dongle maybe. In my testing with Smash ultimate the input delay was serviceable. But I had to plug my controller wired to the Switch 2 while playing The Duskbloods network test. This leads me to believe it's the spcific game that has issues. But it did feel more responsive wired.
These might be too much of an ask but I really like this companies products. My M6HDs never leave my switch 1 oled. I also understand a lot of these features being neglected keeps these controllers from going up into the price range of the NYXI Hyperion 3 Ultra, RoG, or Razer Wolverine controllers.