Correct, should not be built by the first company in line to yield to the NSA while hungry for data. Also, ...
Re: hard, not at all, there are many responsive floss development tools already. They just need some extra polish, community building, and not be written in Java or Javascript, etc.
Probably needs some sponsorship to build mindshare, that seems the harder part.
If too big a request (from scratch) one could start with an existing one and add plugins wrapping existing floss dev tools and language servers at a lower priority.
The rest of the terms such as "responsive," "easy to use", and "no unique interfaces" make your request hard to fulfill