Thanks for that detailed response Andreas - it all makes sense with that.
As for performance optimization (which seems to be the biggest issue for UI5 based on the discussions I'm having with other developers):
With a little re-work, could we not just use script tags to include each control we want to use instead of having to load an entire library and without the need for parsing a preload json file. We could then use standard web tools (with grunt, gulp, etc) to minify an concat resources and so on... and only ever include exactly what we need which miniises the size of the resources and the number of GET requests...
Regards...