@Risker, @Keegan: does "sysadmin" sound good to you folks too? The permissions breakdown is at https://meta.wikimedia.org/wiki/Toolhub#User_permission_levels for reference.

Provided the term "sysadmin" isn't used elsewhere in the Mediawiki world to represent an even higher level of permission than the (current) Toolhub administrator role, I have no problems with this. Please be very sure of this; in many non-Mediawiki settings, "sysadmin" has a significantly higher permission/access level than the current Toolhub admin role will have.

@bd808 do you think this is mature enough to move to groomed or we still need to research this further?

I took my time to research more on this on enwiki, commons, meta and wikitech. Though there group naming convention is not an exact one-one mapping to ours, I think there are some takeaways that can be found here. First, after going through enwiki and metawiki, there seems to be a general consensus that stewards should be the highest level, with permission to perform the role of every other group. sysadmin doesn't seem to come up in my research (we do have opsadmin but this is also low on the hierarchy). For more information on this, see https://en.wikipedia.org/wiki/Wikipedia:User_access_levels and https://meta.wikimedia.org/wiki/User_groups