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Aaaah! So we like spherical aberration do we?
Having said that, there is a thing called a "lensless Schmidt".
You won't have coma, but you will have the spherical aberration. Rutten and van Venrooij discuss this in their book "Telescope Optics", page 82. Trouble is that the focal length of the commercial SCT primary is wrong. Taking a 200mm aperture system a focal length of 1600mm is needed to give a maximum blur of 0.25mm when in focus. System is f/8 which would make the tube 3.2m long as the entrance pupil must be positioned at the centre of curvature of the mirror which is 2R.
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