Im working on a free version of Controlled Flight, ”Controlled Flight Lite”. It is based on the same code base as the full version, but with limited features. Fewer algorithms and customizability is limited.
I think it will contain enough functionality for many use cases and be simple to use. Documentation is here. The included feature set is currently worked on and may change for the release.
It should be published in the Unity Asset Store this week or the beginning of next week.