It sounds like it`s time for you to spend about $50 for a book and some software. The book and the software will show you what the usable designs of the simpler optical systems are (doesn`t go into things like the Stevick Paul design and tetraschiefspieglers and so forth). The book is Telescope Optics, Evaluation and Design by Rutten and Van Venrooij and is available at Willmann-Bell and the price of $50 is for both the book and the software together. My suggestion is to get both as that way, you can evaluage the designs you come up with on the computer.
As far as Cass/Newts are concerned, the primary is normally a parabola and the secondary is the matching secondary for the cass and it can be switched out for a flat set at 45deg. for use as a fast Newt. The cass light path can also go out a 45deg. angle flat near the primary if desired or can go out the back of the perforated primary as desired. Careful design of the secondary holders can allow for them to be swapped out without changing the alignment of the primary.