Cutting the optical tube length in half with a flat mirror and moving the secondary to the center of primary mirror hole is not a new idea and does nothing to help manufacture and assembly. Instead making a single mirror with a binary surface, i.e. one radius at inner zone and another in outer zone, a whole world of manufacture and assembly problems can be avoided. Assembly problems would eliminate themselves, and manufacturing would get easier by making traditional manufacturing near impossible and forcing more advanced techniques.
Commercial astronomical telescope optics development has followed a straight tangent for decades now. Focal lengths have shortened while image sizes have grown. Refractive telescopes houses five or even six lenses, making them more and more like over-sized camera optics, driving up manufacturing costs fast. Producing more and more expensive and generic products for smaller and smaller range of enthusiasts does not pay back development.
Originally suggested by Maksutov, a Maksutov microscope objective (or eyepiece) is a reverse Gregorian type reflective objective. It has high numerical aperture and has corrected spherical, coma and color aberrations. It requires a field flattener to correct the field curvature, but for on-axis observations, it has a long working distance and short total track.
Designing a reflective telescope system with paraxial optics is really easy, since there is no refraction involved. Pre-design calculations offer final solutions in most cases. Here I will demonstrate use of spreadsheet for designing a Cassegrain type reflective telescope.