Their is nothing wrong with creating a new bylaw but it is a bit of overkill IMHO.
Just vote at the next GM by a simple majority to engage contractor xx to clean all windows and remove cobwebs every x months at a cost of $x. This leaves control with the Strata whereas if you create a bylaw the Strata is obliged to continue cleaning the windows until bylaw is revoked via a 75% vote.
Or ask which owners would like to participate in paying a contractor to clean their windows and just these owners pay rather than the Strata.