You just need a simple majority (51 percent) at the EC to decide not to pursue this. I think non-financial members can still vote at EC meetings but not at general meetings.
I would push the idea of the retrospective by-law allowing the changes but conferring responsibility for their upkeep and maintenance to the individual owners.
If the others get bolshie, I would warn them gently that if you are forced to change your window, others with unauthorised changes may also be at risk.