In production we run CirrusSearch against Elasticsearch with a bunch of plugins installed - wikimedia-extra and the experimental highlighter. But Cirrus is capable of running without them. It'd be simpler for us if we simply mandated that they be installed. I created https://phabricator.wikimedia.org/T101029 to talk about it by my current feeling is that it probably wouldn't be a huge hardship to make those plugins required.
Opinions?
Nik