You can use Libretro's native Retroarch core for DOS box. You just have to setup an autoexec file that mounts the game folders as the C: drive (or whichever you want) and then run EXEs from there. I'm not 100% sure if it's still missing keyboard input, but I can check when I get home.
You could also use the PSP version of DOSbox in Adrenaline as well, but note you'll be running it sandboxed with the PSP's spec instead of the Vita's.