For now it's not possible, you have to eat it all. Combined.js has everything, all the widgets that comes with the platform ( either if you use it or not ), and a lot of history behind the scenes ( as it has more than 5 years ), hard to touch it without breaking anything.
We had developed an HTML5 mobile App with ionic platform, using just TW REST API, it's fast, efficient and mobile friendly not like TW Mashups. TW Mashups are not designed to be well used on mobile, building mobile Apps with TW Mashups it's not a good approach.
PTC has another product to build mobile Apps using TW, it was a project called ThingX for which we had really good expectations but now it's on Vuforia Studio, they moved away from TW platform but it's totally integrated with TW. I don't know if it's yet officially released or not....
I was actually invited to ThingX beta program. Couldnt participate for time reasons though.
Since we have had to move our AugmentedReality projects we could not wait for it. So we are using Vuforia+Unity+TW. We have made a simple WebBrowser which is seamlessly called from within the AR App. Now we have added a general barcode scanner which contains cyphered URL to specific mashups and this combined.js slows the whole UX down.
Anyhow thanks for Info.
I am working on a script, which would delete all comments from that JS file, we will see how small it gets....