The likes of PMI and IBZ along with ALC and AGA seem to be 'fillers' to keep aircraft utilised at the weekends (they are all only Sat/Sun) when the demand for the more business focussed routes is lower, and BA have obviously worked out that they'll make more money from fairly full leisure routes than half full business ones!
I would've thought any s/h reductions to allow for more l/h would be removing whole daily flights off of some of the higher frequency routes, rather than freeing up some rather random weekend slots.