That's too bad, the FlashAir card works exactly how I would expect in this case - drag and drop files to the SD card over WiFi to the FG99, hit its reset button and good to go.
What sort of "other applications" are you envisioning that would require the cartridge port? Why not use TIPI?
Drag and drop TO the card is nice, but what about download FROM the card back to the PC or delete? I was never able to get it to work so I don't know if it had that functionality.
What other applications? Well, Stuarts Browser, and/or a future version of TIMXT, and other unknown things...
...gotta leave for work now, so I'll be off line for a while.
Why not use TIPI, not everyone will have one and not everyone will be able to afford one, just thinking of others too.