"WDQS can be run as a service for any Wikibase instance, not just Wikidata." — I found some quite simpler documentation for WDQS, let's try to set up one if possible.
I found out that it is simpler to follow the instructions laid down here and the one laid down here.
We can gradually do this if possible.
There's only no native support for multiple wikis so this would be 6GB memory needed and a fair bit of sysadmin time.
After a short discussion on IRC, I think it's best that this is declined for the time being. We don't have many resources to spare and without a larger number of people asking for a service we can't afford to spend 6GB memory on such a project.