How so? Doing this with modern OpenGL would be much simpler than the software rasterizer solution.

I think I'm gonna have to do it anyway, because some players claim they get nausea when playing at such low resolution (320x240), and the only way to give them higher resolutions that perform reasonably is to have it hardware accelerated.

Renderer is abstracted away already, but the real difference would probably be occlusion culling... With raycasting, I get it for free, but if I'd go down the hardware accelerated path I'd have to pick something more clever.

Raycasting and software rendering in general tends to scale poorly with resolution, even with vectorization and all the bells and whistles of modern CPUs.