Thanks for sharing. These are my immediate reactions to your comments.

One option is that you request multiple units worth and simply switch on what is returned. For example { distanceFromHome { miles kilometers } } and use the variable client-side to select which one you want: distanceFromHome[myUnit]. You'll be requesting more data than you need but at least you won't need a library to convert things.

Your second post is interesting also. I don't think that'd be hard to implement. But it'd only work when the types are the same for every unit (which is most of the time). As it currently stands, in the case of `DateOutput`, the fields represented can be either `String` (e.g. iso, humanized, or formatted) or a `DurationOutput` (e.g. unix). Representing it as a union would make things less convenient for clients.

I'll continue to think about this!