In M1#11, @jack wrote:

There are some more options in there, actually:

• extensions (sic) -- this feature exists in the code, sorta, but it was never written so you can't currently choose to enable e.g. SocialProfile during wiki creation. It's definitely something we want to implement in the future and frankly long overdue.

Per above, we should decide what extensions we want to allow the users to pick during Special:CreateWiki process. There's some extensions that probably require manual/special configuration, so those extensions won't be able to be on the list.