According to the manual, no. The pedal outlet seems to be specifically designed for the set it comes with. With luck, the plug might work as a regular MIDI in so you could connect a MIDI board to it (like a Behringer FCB1010), but I wouldn't bet on it.
You can always use a non-keyboard-specific pedal. The Boss FV500 is pretty nice, for example.
If you're set on the FC7, then according to the chart here (bottom of the page), the only one that seems to use them is the P-155.
By "non-specific" I meant a standard volume pedal for guitar (two INs, two OUTs - perfect for the YDP). It wouldn't work on the internal speakers though, so yeah, you would have to get some more gear to get around that... But add a 4 channel mixer to those external speakers and you could run your guitar through 'em, too!