Can we use low-end front derailleur with an 11 speed crankset?
Any 2x front shifter has only two or three clicks and as long as the cable pull isn't wildly out of spec an X speed derailleur will work with an 11 speed crankset. If you have just a double in front the key thing is that the cage curvature match the size of the large chainring and you can mount the derailluer with the appropriate clearance (roughly 3mm between tooth tip and derailluer cage). I have successfully shifted 11 speed double chainrings in in 50/34, 46/30 and 38/22 with 9 speed front derailleurs and Campy 10 speed brifters. Having a chain catcher like the K-edge one helps a lot. 

Triples are more fussy when it comes to matching derailluer cage and shifters. 

It's almost never a question of will it work, but will it work smoothly enough for you. Mix and matching components will always require a bit more fiddling and likely will not ever work as smoothly as fully matched high end components. But it's just a bike, enjoy the ability to hack and bodge things while you can.