You wouldn't.
en.wikipedia.org
There is no decision to be made, Apple simply does not allow it.
On top of that, Apple has entirely removed hypervisor support as of iOS/ipadOS 16.4.
I also prefer 2x5K@27". But guess what is also not a great experience? Carrying around more hardware than necessary. There is always a tradeoff, and for mobile computing I will choose small and light over a bigger screen every time. Again, I used an 11" MacBook Air exclusively for mobile computing for years, and it was fine. I use my 11" iPad Pro for remote desktop now, and it is fine.
Why would it need to be a case?
The Logitech Keys-To-Go is 180 grams, less than a third of the Magic Keyboard, and the Targus Ergonomic Foldable Keyboard is only 140 grams. If you want to go really extreme you can get a tiny rollable keyboard.
Personally, I always choose a mouse over a trackpad, so for me the integrated trackpad just adds weight, bulk and annoyance.
Also, besides the benefit of only needing one device, the whole point of using an iPad instead of a MacBook is the ergonomic benefits of having the keyboard detached from the device.
If Apple made a spiritual successor to the 12" PowerBook G4, 11" MacBook Air and 12" MacBook now that they have the chips to make such a device truly amazing, that is what I would use as my sole mobile device. However, I would lose the option to use an iPad as an iPad, which is what I would want to do most of the time, and that would suck. Being able to simply fire up macOS in a VM only when I need it would be so much better.