I understand the concept ...
How the cuts would be made with accurate spacing is where I get lost. When using the saw in the normal position, the work piece is indexed using a jig in the miter slots. Having the blades horizontal with the saw attached to the wall will mean you need a jig or sliding fixture to hold the work and keep it from bending downward as well as moving it accurately on the index block. It can be done, but you'll have to sort out all the issues above.
A router would be much easier as suggested. :smile3:
A different joint may be the answer....?
A radial arm saw with the blade horizontal may be a solution?
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)