WMCS is indeed not a general purpose MediaWiki-hosting platform (there are already hosting businesses for that), but MediaWiki could be hosted for projects that follow the terms of use- some of them may not be immediately apparent. For example, if
translatewiki.org wanted to be hosted in WMF Cloud, I think everybody would be happy, as it is the main tool used for Wikimedia project translation, even if it is also used for 3rd party ones. Several communities (e.g. Wikimedia user groups) are offered cloud or even production wiki hosting if they are key to the advancement to the mission:
https://wikimediafoundation.org/about/mission/If you believe someone may be violating the terms of service, to the detriment of the community, send a notification in private to the Cloud Team and they can have a look.