Geohack is one of the tools that is used by readers (in contrast to mainly by editors), as most coordinate templates link to it.
This extension effectively already is Geohack's code wrapped in a MediaWiki extension. It needs some updates and maybe enhancing to support the features that have been added to Geohack since, but IMHO the way to proceed on this matter.
I'll note that wdq-mm / ORES didn't do too badly during the big bad NFS outage. Those are puppetized, have monitoring, and do not depend on NFS in any form or way. We can do that for geohack too if necessary.