The addition to include framebuffer took several hours to compile on my 2 core laptop, and made next to no difference in the final vmlinuz/modules size. Perhaps a kernel .config tweak that might be made for future Fatdog versions?
I've set up my desktop system to use 640x480 resolution, and for me that's a vga=0x311 boot code (as indicated when booted with vga=ask) to have my laptop boot into the same 640x480x16 vesa resolution. At such low resolution running on both the laptop (framebuffer) and desktop (Fatdog DVD booted) the responsiveness is great, near as good as being at the desktop directly.
I actually used busybox init to boot i.e. the last command run in init is to exec /sbin/init ... where that is a sym link to busybox init, with no /etc/inittab busybox uses its own internal version that includes setting up several terminals (ctrl-alt-F1 .. F2 ...etc).
Sharing the same framebuffer is interesting if you have a vnc'd graphical session (i.e. into full Fatdog desktop on my desktop system) running a video running on say Ctrl-Alt-F1 on the laptop, and are viewing Ctrl-Alt-F2 as a terminal session - as the video 'bleeds' through, so you end up with a textual cli session, with the video also showing, wherever that might be placed in the gui session. With the version of fbvnc I compiled/used ctrl-L stops gui activity i.e. kills the 'bleed through'. Left running and not only does the video bleed through, but also any other changes, such as the clock minutes changes.
I have no actual measures, but the general feel is that fbvnc through ssh that uses compression, seems more responsive than tigervnc that uses its own compression.
With a bit of trickery, I suspect you could set up that vnc with a video showing on part of the desktop and all other fatdog items (tray etc) hidden out of view, and where that video window could be sized/positioned to 'fit' in with tmux panes being used on another terminal - so it looked like you were running a terminal/cli tmux session but where a video was playing in one of the tmux panes
