Interesting, I wonder if those external 3.5" diskette drives will work with this ?

If they're USB, they should! At least the Apple/Oric software supports USB flash storage, and the USB floppies are the same protocol.

The problem is Apple II 3.5" disks are in GCR so you would need a custom controller (IMO certainly doable with an RP2040 let alone RP2350) that is not bound to just PC formats.