A lot of questions . I guess the thought behind this is as following: you're competent or you're not. Unlike the badge awarding system in Moodle (where you can modify criteria based on which the system will award badges or retract them), the competencies don't allow for this. There's no going back on being competent.
I guess the same goes for the second question: once a student receives a competency rating, the only way to delete or undo it, is to remove the competency (framework) altogether.
As for the requesting of features, this can be done in the Tracker. Make an account, find the Competencies bit under the Moodle project, rate or follow at least 4 tracker issues to prove you're a human being and you can request these features to be added. This is however subject to peer review and comments from the Moodle (dev) community, so there's no garantee the features will be added.
IMHO, I doubt these features you described have any added value, but that's only my take on the subject.