I'm not sure there any such things as 'Ridley's rules' exist for the '
Alien' films. From what I remember, the only thing he truly laments about the direction the series went, was that it didn't return to the derelict and demystify how it became like that.
Something which '
Prometheus' didn't really do, either, as it turned out.
He can be a gifted artistic visionary (although, not always), but a part of that mentality is being extremely fluid and distracted by the newest ideas which come his way. Even in the post-production interviews for '
Prometheus', it was clear he didn't have anything approaching concrete plans for the direction he wanted the series to head in.