I think it's good if admin can create widget and use widgets in templates in MyBB 2.0 (like vbulletin5 and wordpress)
Disagree - remember that MyBB is not CMS. It has to be maintain in compliance with KISS model. Any other additions like widgets/relays etc would make it more CMS-like, Its not what developers want.
Maybe it would be a good idea to include content from other CMS systems. A REST-API could enable embedding of any kind of snippets/widgets/content from every supporting CMS to MyBB 2.0.