Actually I have the VT240 firmware ROM dumps, that's where I got the original font from. The problem is, at least the VT240 is a rather sophisticated thing, with a T-11 CPU, some additional MCU, and a graphics accelerator chip. There is an extensive service manual available, with schematics and everything, but properly emulating the whole firmware + all relevant peripherals is non-trivial and a significant amount of work. The result is then a rather slow virtual terminal.

There is a basic and totally incomplete version of a VT240 in MAME though, which is good enough to test certain behavior, but it completely lacks the graphics part, so you can't use it to check graphics behavior like DRCS and so on.

EDIT: I also know for sure that there is a firmware emulation of the VT102 available somewhere.