STM32F4 FSMC 8-bit data width with 10+ bit addressing
Unless someone has specific experience that they're willing to share then I suspect you're going to have to just have to (as a crusty old electronics tech I used to work with liked to say) suck it and see.

I've successfully used an STM32F407's FSMC with separate 16-bit data, 16-bit address buses to interface to a Spartan-6.  Both parts were BGA, so I covered my bases by attaching pretty much every FSMC control line to the FPGA as well.  Along those lines, if you have spare I/O (and the FSMC pins aren't otherwise occupied) then I'd suggest wiring it to allow separated address and data buses.

One thing I should say is that I wasn't overly impressed with the blinding speed; iirc (without actually checking my STM32 code for the FSMC settings) I can read and write reliably at around 12MHz, versus 168MHz CPU speed.  That's a lot faster than SPI would have been, but it's not exactly closely coupled.