New DIY Anamorphic Lens design, possible cheap CA correction?

Not to rain on your parade. The problem here is that both the trophy and the French prisms are made of the same material (BK7). Only the angles are different, so at best, you might succeed to reduce the CA (a partial cancellation), though you will not eliminate it.

You might have better results using 1 Perpex and 1 glass prism to make your new prism. Of course bonding is required as well or you end up with horrid reflections on screen.

To eliminate the CA, one of the prisms NEEDS to be made of a different material and have an angle of such, that it now has the same refractive index as the other prism in the doublet. With the apexes opposing, basically, you have an optical version the same as if 2 equal and opposing forces combine, the result being cancellation, and that is the goal here.

This is in part is why the original liquid filled VCs that were made at DIY Audio used water + oil. As it turned out, a VC needs not be CA corrected as badly as a HE because the CA runs horizontally, not vertically like it does with HE lenses and because a VC compresses the image, you don't notice it as much.