In the aircraft I've flown, pilot's seat MEL's have read as follows:
Recline Function - Seat shall be upright
Lumbar Support Function - May be U/S
Armrest - May be U/S
And in all cases the seat function shall be classified as acceptable to the individual pilot.
However, no mention of footrests. I would suggest common sense applies as mentioned previously & the PIC's judgement as to whether to accept an aircraft as serviceable or otherwise.