The loctite might hold it but you do need to take it off again sometime perhaps!
Yes a small, and sharp, cold chisel on the frame mounted male part, it doesn’t have to be perfect. Then pick up some grooves in the footrest by chiselling down the hole, and not remove any metal, whereas a hacksaw cut will take metal away.
If the slack footrest flops around when first tried then add some shim metal sheet of 0.005″ thickness (suggested size to try) around the male boss and hammer the footrest on. Then tighten well, if it is at all slack it will rapidly loosen again.