[Dave]

Maybe this will make it clear on why it's so hard and time consuming. The first issue is that newer versions are not backwards compatible with any of the existing vBulletin and BBCode plugins. All plugins that provide custom implementations into the editor will break and there's nothing that can be done about it aside from porting their CKEditor implementation to the new version. There is no global fix for that. Additionally you'd be required to overwrite existing vBulletin files but since there are no updates anymore that is probably not a big deal.

We basically have 2 options:
1. Editor that is not connected to vBulletin's options and internal code, no attachment manager, no image uploader, etc. Only used to submit simple posts with just text. Probably a few days of work.

2. Editor that implements vBulletin's BBCode to provide support for permission manager, attachment manager and image uploader, etc. Along with that we'd have to make sure that implementations from old plugins need to be rejected since it could break the editor. Probably several weeks of work.

Since no one in their right mind will work on it non-stop and putting a hold on their actual job that gives them money, it will probably take months. Then what will the payoff be? Since vBulletin is not as popular as it used to be it will probably be a couple users saying thank you and the rest leeching off the download and never seeing them again, as expected.

Could it be made into a premium plugin? Probably, but personally I wouldn't do that.