You can set the FS inputs any way you like. It works with pretty much any footswitch (latch or momentary, plus you can reverse the polarity in the settings) and EXP pedals. So you could have, say, FS4 (referring to the Stomp here, the numbers vary on the Floor/LT/Rack) act as a switch and FS5 as an EXP input. Pretty much any combination imagineable is available, so I can't see why the Hotone wouldn't work. Yes, it takes a while sometimes because the menus are small and not on one preference page (in fact, they're in 3 sections), so that might be a little confusing (it was for me), but it's all there.
The very thing lacking is a global curve parameter for the expression pedal, the only thing allowing for adjustments would be the volume block (and it's just linear and logarithmic you can select), so you're pretty much at the mercy of the EXP pedal maker. I really wish Line 6 would add that. I could not use an external EXP I had around as a wah because the curve was just so bad.