I'm reporting back on my attempt to use the Neos on my Swift. Short version: it can work, but you'll need to find the appropriate fixing bolt.

There is an appropriate mounting point on the rear dropout where the stock derailleur hanger attaches to the frame. The problem was finding the right fixing bolt that would go through the Neos derailleur and bolt through the existing opening in the dropout. This probably could have been solved, but I wasn't too keen on using this derailleur once I found the other problem with the Neos.

The Neos is a reverse pull derailleur. A.K.A. "Rapid Rise" or "Low Normal".

This would have for sure driven me mad when switching between bikes, and was a real deal breaker for me.

BTW, this derailleur weights only ~220g (analog postal scale) instead of the 320g claimed by a previous poster.