A) allow a directory ignore cfg
This has been already discussed, and yes, we'll add a feature to create a "blacklist" of folders to be ignored, if this is what you meant.
B)allow only the edited ade be rescanned by gsx and not the entire scenery database
This has been already discussed and no, the issue is, when there's an extremely high number of files, it takes time just to check if something has changed. This will be fixed by adding the aforementioned "blacklist" of folders that don't contain AFCADs or (even worse) are "clones".