Replacement windows

Whilst redecorating the Lookout Tower / signal box, which forms part of the Heritage Centre, the contractor discovered that many of the windows had rotten sections due to the use of softwood. The previous attempt to decorate seems to have just applied a single coat over already flaking paint.
Four of the windows are actually beyond repair, and repairing the others would only bring a temporary respite. Their recommendation is for total replacement with hardwood windows.
This is an urgent need, given the approach of winter.