Units and scale, and how they correlate, are extremely important even in a light weight, portable format. Actually, probably more so in one than in a more complex scenario.
You can't assume people will not care about those because their workflow will be independent of it like yours was for a few example productions, because very frequently they won't have the choice. As an interop format that deals with external contributions (rendering engines and so on being heavily dependent on it) you WILL bump into scale factors whether you like it or not, and the format will be rendered useless by not having control over those when it'll happen. There are things one omits or includes for the sake of forecfully encouraging good practices, those are practical-philosophical choices and are fine, and best made by a benevolent dictator for the project (any half decent programming language out there has craptons of those, and they are important to give languages and format identity and coherence). Scaling and units are not one of those, they are a fundamental requirement implicit to what you set off to describe with these files.
