That was very comprehensive. I'm also a VR Doomer, though not quite as experienced. I started uploading videos of Ultimate Doom and Sigil to YouTube and Rumble. I like your idea about using secondary buttons for weapon selection. That had not occurred to me.
You are right about the little baby hands in the Alternative Vanilla 3D Weapons pack, but there is a way to re-scale the weapons. If you go to Options > VR options, there is a setting called Weapon Sprite/Model Scale, which if changed to 1.00, will resize the baby hands and mini weapons into adult hands and full sized weapons.
It's also useful to have a button mapped to moving forward in a perfectly straight line, similar to the W key on a keyboard. I have found it essential for platforming, since moving forward with the thumbstick will almost always have some unintended left-right movement, which is hazardous in a level like The Chasm.
My links https://rumble.com/user/RoxOfBockets https://youtube.com/@RoxOfBockets/videos