I never used GuideTours either but, in my opinion, that would be a nice way to provide:
- a general overview (what each special page does, even though their titles are self-explanatory) about ManageWiki;
- some useful information (example: warning about how messing up with group permissions can break the wiki and when that happen, users can reset the settings);
- walk-through guides on how to do things like enabe a extension/skin, change the logo, create a new user group (example: moderation) and assign users to that group.
GT looks like it can be enabled ext-side and wiki-side.
I do not feel this can be designed on a super broad empty extension like ManageWiki. A proof of concept should be made and then pushed into something like MirahezeMagic.
It could be, though it'll be something someone from the community choses to take on rather than me. Perhaps even bringing it up at https://meta.miraheze.org/wiki/Community_noticeboard would get interest and ideas.