the vector crt signals are too fast by a factor of six or more for even the best galvos, you'd have to recode the source to add delays, considering, if this is a vector game, the vector generation timing and scaling is always partially hardcoded in hardware,so you have a BIG problem. Also crts don't have blanking points, buffer points, extra corner points, all needed by even the fastest galvos, and most vector systems, with the exception of a few that do sliding stroke writing,(ie charge a integrator to the new point voltage) return to center in between objects, the return to center is fine for a blanked electron beam, but it confuses the heck out of the galvos. btw, as you expand scan size, you need to slow down the scan rate.
galvos have inertia,electron beams for practical purposes dont.
the other way to do it is use a AO deflector pair, but thats megabucks.
I know the fellows that did laser mame, and its not easy. plus if your using game code, its a most excellent way to get sued. Laser Mame passed the points from a emulated game to a pangolin card that drove the galvos, and that is probably the best solution. Galvos limit out at about 700 points in a image.
if its military, like a flight simulator, start here:
if thats not fast enough
neos makes a nice 512x512 XY deflector, so does
probably Crystal technology and Brimrose do as well.
none of the mentioned hard drive motors, modified speakers etc will get you anywhere close to the speed of a true galvo with feedback I used to earn my living doing vector graphics with lasers.