I've enabled dynamic vsync toggling and vQuake 2 should work with or without it.
I'll get you a build shortly. There's a lot of logging in there to fix the ICR2 in game hud (Note the last commit to dosbox-Rendition is pretty old. You won't be able to get ICR 2 up and running without an updated build.)
If you don't mind the logging, I'll get you a build with the fix. Usually with vsync the buffers are swapped and then V_FIFO_WAIT_DISPLAY command is issued to freeze the chip until vsync has completed. In RReady's case vsync is already enabled by the time the swap command is handled.
My fix involves starting out with vsync disabled, (unless forced in log) and then enabling it after hitting V_FIFO_WAIT_DISPLAY. V_BitBlt is what vQuake 2 uses in nopageflip mode. I've added support for that as well.