I have written termcap and terminfo entries, and I am a vttest contributer. I admit that I haven't yet written a terminal. I've owned a few physical ones: VT100, VT220, VT320, VT510, and some awful Televideo thing.

I do restore snapshots in random orders, and I really want my terminal to know exactly where to resume. I don't expect the terminal to guess. I expect it to accept a blob of serialized state data, and of course I also need it to produce that sort of data on demand. I want that data in the snapshot files that my emulator creates.

I could indeed put the emulator, along with separate terminals (xterm) and the OS they require, within an emulator. This works, but adds the overhead of a whole extra OS. It gets confusing to use, takes up lots of memory, runs slowly, and takes up extra space on the screen.