I like it. I've thought about this very design in my mind many times. Will it make your 8-3/4 stronger than a 9"?... no, but it certainly can't hurt.

My 8-3/4" has a moser backbrace, Williams main cap, Dr.Diff spool & 35-spline axles. To the OP: If you build this, let me know with a PM. I'd like to see how it comes together and may be interested in one.