Depending on server application you are using, there are mechanisms to compress files at the server level. This doesn't help developers who need the uncompressed versions to look at code, but in production environments, it makes a huge difference.
In Tomcat, this is pretty easy - here is a simple example: How to Compress HTTP responses at the Tomcat level | Jaspersoft Community
Also, when it comes to Widget Extensions, the JS and CSS files get copied directly from the contributing files into the combined files. So, if you are writing the widget, I would encourage doing a minify of the JS and CSS code to help the overall size. Also, If you see specific areas in the combined js and css files that is large and being contributed from other widgets, I would encourage you to get in contact with the extension Author and let them know that is something they could do as an improvement, which would help the community out in general.
These are kind of generic suggestions, and are more of a workaround for the problem, but they can make some immediate difference if you are having problems now while Thingworx development works on making this better for the future.
