Hi, thanks for your response.
I understand what the memory cost would be, and I've decided it would be worth paying that cost for my project. I am sorry to hear that the architecture of your project is a limiting factor here. I know all too well what it can be like working in a legacy code base; you have my sympathies.
Unfortunately, using a 1x1 tile would make my map editing workflow 4x more tedious, so that will not work for me.