Where to put the status bar (for any bar, really) depends on monitor height. Also, you can run mpv in the TTY, but you probably know that. You can't run it inside of a multiplexer, but MAYBE there could be a way. Like, I have been working on my system and have been wanting to integrate tmux into it, so I have this script for running X programs inside of tmux:

if echo $TERM | grep "tmux*" > /dev/null; then
tmux run-shell -b "xdg-open \"$1\" > /dev/null"
else
xdg-open $1 > /dev/null
fi

You could maybe make something like this for the TTY. Maybe that creates a shell in the background, and detaches tmux, runs mpv, and then reattaches afterwards.

There was also directfb, you may be able to use that. I don't know anything about it, but maybe you do because you have been using these systems for longer and was around when this was more of a thing. But apparently it can do windowing. And also, GTK and Qt both supposedly support the TTY, and I think it might be through that. Not sure, but I have seen a picture of Firefox running in a multiplexer, in the TTY. You can also run sdl in the TTY.

Also, fcitx is in fact possible, I remember seeing that as well, and there is a package called fcitx-fbterm-git in the TTY that you may want to check out. And of course, there are image viewers like fbv, and PDF viewers like fbpdf. And there are alternatives to fbterm as well, like mlterm and yaft (both support sixel images, and mlterm is also an X terminal emulator, and it can actually do vertical text, which is kinda cool, and it has an option for using it with fcitx, though I'm not sure that it works in the TTY).

This is all pretty obscure information, so I don't know much about it. Post still ended up gigantic, though. But I personally just use X. Has the advantage that everything is guaranteed to work in it, and is also portable, while framebuffer stuff is a lot more OS-dependent. The problem is that none of this shit is actually integrated, programs all conflict with each other, because these OSs are still basically 70s mainframes and can barely handle monitors correctly, and really would rather use punchcards instead.

May try this stuff more later, but for now I'm busy trying to come up with a set of keybindings that don't suck and that are actually ergonomic, and that I can apply universally, while also preserving defaults and avoiding conflicts (by focusing on the Super and Hyper keys, and also using key sequences after a prefix key, in some cases to switch between different key maps), and integrating all of the terminal multiplexer shit, and all terminal programs (that can't even consistently use all modifiers).

StumpWM and X are making that a lot easier, by translating keys to other keys, and also conditionally translating bindings to other bindings, depending on the selected window. Also, testing framebuffer stuff will really have to be on another computer, because testing that, I have frozen my computer multiple times to the point that nothing could be done and I just had to pull the plug. All inputs were ignored. X may be bad, but it's less bad than the OSs it runs on, so I have accepted it.