Can you use a cube dichroic beamsplitter rather than a tilted plate?  Tilted plates in converging or diverging light introduce additional astigmatic aberrations that cube beamsplitters don’t have.

Another solution is to introduce a second tilted plate with a toroidal front surface and plano rear surface.  Optimize both toroid X,Y radii and the tilt angle.  Depending on how the first plate is tilted, either the toroid radius or radius of rotation may be set to infinite, making the second plate into a simple very weak cylindrical lens.  There are several journal articles on this, such as in Applied Optics, Vol. 54, Issue 7, pp. 1758-1764 (2015).