How to use the Bangle.js Layout library

Would it be bloaty to add setLabel

I think it could be a good one to add, yes. It's could also provide some extra logic in there as sometimes new text might change the width of the field which could move other things.

there is lot of "Bangle." calls inside

It's only to handle the touchscreen so they could always be put inside if (global.Bangle) ...

If you're wondering about it for other smartwatches I'd definitely say you should try including jswrap_bangle in your builds for those so the Bangle.js stuff is exposed

edit: I should also add that I'd like to make the layout/rendering for this really fast, so when we get something that works well for what we need it for I may well build it into the firmware - and then it could make sense to use it because it'll actually be faster that issuing draw calls from JS.