"It would probably be just as easy to recreate a RISCOS-like OS from scratch (perhaps making use of some freely available components), and re implimenting the API. I think that this would would be about same amount of work and produce a better result."
I think it's important to distinguish between the factors that keep people using RISC OS: the desktop environment and the applications.
Contrary to popular opinion, the look and feel of the RISC OS desktop could be recreated for other desktop environments by skilled developers in a reasonable amount of time. Porting the whole thing, or reverse engineering then duplicating it, only makes sense if you want to use legacy software or want to retain familiar APIs, and that could be done via an emulator.
For most users, the only thing stopping them from moving to another desktop environment that looks and feels the same is the lack of familiar applications. Basically, if you could port the most popular applications to such an environment, you would satisfy many remaining users; the less popular applications would just have to be run in an emulator.
This approach is different to the usual one people fear in this forum: we're not talking about running ex-RISC OS applications on Windows and occasionally firing up an emulator; we're talking about running ex-RISC OS applications in a familiar environment and integrating an emulator to make sure all the niche applications continue to run.