Cool!
I'd say move the jumpers and DIP switches off to one side, most people are lazy (ok well maybe just me ..) and would not remove the carts from the board while trying to fiddle with the jumpers and DIP switches this runs the risk of over stressing a cart in it's slot.
Also put in the BIGGEST switches you can, nothing worse than fiddling with DIP switches with the end of a pen (ala back of 1541-II drives) .. plus all us "enthusiasts" are getting older
Being able to swap the IO1/2 lines is a good feature of the Fotios board.
The ability to easily (and completely) disconnect a board from the bus without removing it would be handy so that if you have 2 board that don't play nice together you can turn off one slot ... one big button per slot ?
And how about an option ROM socket ? Maybe taking up a pseudo "slot 4" with a bank select for the larger EPROMS ?
One other thing ... I've read that the C128 has a "noisy" bus ... is this noise something that could be cleaned up or filtered by some cleverness on the expansion port ?
Anyway .. whatever you make will be nice
Regards
Mark