Can you? The last I looked at it (a year or two ago), the vt220 in MAME was just the beginning skeleton of an implementation, and it doesn't seem to have been touched much since then. A shame, because AFAIK no "terminal emulator" implements vt220-style sixels (which are different than than the widely-implemented vt4xx-style sixels).
The really interesting ones are VT340 variants with ReGIS and full SIXEL graphics
VT340 is definitely interesting and if someone were to emulate one that would also be great! (there's been some good research, e.g.: https://github.com/hackerb9/vt340test, which you might be surprised to learn has been used to make Windows Terminal one of the more conformant terminals...)
Funnily enough, the one VT510 I had for some time actually came from a VHS rental place that for reasons unknown to me ran Blockbuster Video customized VAX 6.1 on Alpha (which I also grabbed). BBV was not very well known in Poland, but this specific machine had unwiped disks and logs showing it was used from 1996 to 2000, then it was found lying in a corner when a moving service was asked to clean out a location after a tenant that came in after the video rental.
There was probably a DECserver missing somewhere in the pile before I got my hands on it ;)
I would avoid doing the PTY thing and instead do this (works on WSL if MAME is the windows version):
You can do the same thing with a vt220.I've had an idea to try to write a sort of high-level-ish VT220 emulator that pokes and patches the ROMs and the system to let you control it with the mouse, paste and stuff, lets you just doubleclick it to get a terminal, etc... I forgot about that until seeing this. Nobody would use it for more than 5 minutes but it would be funny.