You can use the various built-in scalers to stretch the image to a specified resolution. Gulizoka's builds supports pixel shaders, too (with the "direct3d" output method).

It won't work in the way you are imagining. There is a major difference in how 3D antialiasing is accomplished on 3d displays versus blowing up a 2d image - in the 3d version, you have points at each corner of the polygon, giving you a reference for the line that needs to be drawn between them, and cards take advantage of this in establishing how to "fill in" jaggies on an aliased line. So one of the most popular antialiasing techniques is super sampling, where the entire display is rendered at 2x resolution and then reduced, providing extra information to smooth things out.

In a 2d blown up bitmap, there is no easy way to determine what is a valid off pixel and what is "missing" in a jaggy line. You can render it at 2x, but you still don't have hints on which information is just missing versus completely not drawn on purpose.

There are a bunch of attempts to correct this in the current Dosbox, you should check them out. But just turning on FSAA in your video card won't make a difference, is the point.

-Frob