Here’s someone who already made one, so I think it’s possible for sure. There are also people who have already made pseudo-all-in-ones already by sticking a mainboard onto the back of a monitor. Similarly, someone is working on a 2-in-1 here.
You might be able to easily modify an off-the-shelf monitor if it has enough room in the back and then cut a few holes in the chassis to install the USB-C ports to extend to the outside (plus a power button, see Input Connector Shim for a way to do that).