I'm tempted to put together an FPAA with Tiny Tapeout, but it likely won't fit in the allocated area.

TT allows you to pay more and build multi-block designs

Check the switching speed specification, and shared i/o bank configuration.

The project has a narrow scope of use-cases. =3

Switching speed: should be good enough for audio in the kHz range, even for off-chip control.

Analog i/o pins: definitely limited, even if you purchase the highest option available (6).