As I said in the link, I'd evaluate them on a case by case basis if reported. In general, they won't be changed because it can theoretically come up in tons of places if people change style properties.
This place will be changed as we don't allow changes of admin style properties (by end users) so the flexibility needed won't apply here.
Probably the best way to solve this is to parse all CSS when at least one property in template doesn't exist, then just remove broken CSS properties in the final CSS. But yeah, that'd require a lot of coding and debugging.