Well, the way I look at it, is when you are playing an organ chord with one hand, a synth lead with the other, what are you using your other limbs for? How are you going to switch Leslie speed when both hands are busy?
Here is a picture of my rig. Montage 7 on the bottom, Korg Kronos on the top, NUC PC running Cantabile in the gig rack (along with Nord G2, Mixer, Scarlet 2i4 USB, DMXIS interface and IEM transmitter).
But look at my foot area! Here is the FC300 in all its glory along with extra pedals and switches to keep my feet busy....
From left to right, the pedals (2 and.3 on the FC300 to the right)
1 - Organ Swell
2 - Volume (e.g. the fade in/fade out on Shine On You Crazy Diamond)
3 - Leslie Fast/Slow (or other modulation)
From left to right, the switches (4 and 5 on the FC300 to the top middle)
1 -Click/Backing Track start (usually the guitar player or drummer has this)
2- Manual DMX light step (my DMX light show is usually automated, but some events are manual. E.g. Start of Shine on. Fade stage left for keys. Then fade stage right for guitar, then fade out before main song start is all manual before we kick the backing track in, which then controls the DMX cues
3 - DMX Hazer, so I can fill the stage with haze for the lights when I need a boost above the background haze production (and annoy the backing singers who reckon the haze dries their throats!

4 - Depends on the song, but for example on “On the Run” - fades in the sample I use to bridge between Breathe and the On the Run Performace
5 - As above for (4), but starts/stops the “On the run sequence”
So consider Shine On. I have so much to do, holding on the massive left hand chord (10 layers in the Kronos and Wine glass samples on the Montage), single note effects or lead on the right hand, so how do I trigger light cues and fade in my sounds when both hands are on the keys? My feet of course!
And all the FC300 is doing is producing MIDI data into the rig according to how I have programmed it for each song. But you will never get this flexibility from an FC7 connected to your board. this is why the FC300 is so critical to me.
This (using my feet philosophy) is why my first instinct is to get the macro controller behind the super knob on a foot pedal!
This also shows why my FC300 is so indispensable. I have had it for 11 years and could not be without it, despite having changed my keyboard rig. Indeed, I have just acquired a second FC300 as a spare (as after the 10 year point I start getting a little concerned about hardware reliability - and the gigs I do must carry on if you do get a failure). Amazingly the FC300 is still sold by Roland in its original form that I purchased in 2008, and it was probably on the market several years prior to that - which is amazing longevity for a hardware product these days - it is still in demand.
It is not cheap (Behinger FCB is cheaper) but it is so versatile, and.a relative bargain when you amortise it’s cost over a decade (at least) of ownership!
And of course, I m switching patches using the FC300 switches closest to my feet (along with bank up/down switches on the top left). Because the Kronos and Montage so smooth sound transition/switching (and Cantabile on the PC will also do it to a degree for the VSTs I use) it means I can play sounds with both hands and seamlessly switch to new ones without taking my hands off of the keyboards.
Hope that gives sone ideas on why you should not let you feet go idle in a gig

And of course with both feet busy, as well as arms, it means I have an excuse to sit down ... like the drummer!
Love your feet as well as your hands.
