Yes, DOS-version made me a hater of it.
You're a tough guy if you really consider a complete re-build.
Afair, in more recent environments, allegro is shipping renderpathes to DX or GL, if possible. There is no such accelaration on Amiga. 800 Mhz vs 50 is a real showstopper.
Thumbs up for your efforts
p.s.
i had a look at this acs stuff. some of this, if allegro is really part of it, is 2d only. a port shouldn't be that hard, but then speed limits, restricted resolutions, and all of it is chunky mode. phew.