sure, and that's good. we can definitely use one.

couple things to note:
* passes/mountains shouldn't be moved unless there is a reason - we've been trying to get these aligned with the latest 3dep lidar scans, which are unlikely to coincide with administrative boundaries. moving Arc Pass, as an example, puts it quite a ways to the south of the true saddle point 
* adding them to the boundary makes importing boundary updates somewhat more tedious/annoying and (tool dependent) can break the somewhat questionable practice of linking these nodes from their wikidata entities
* the Sierra runs much further north and south than is currently modeled
* type=multilinestring isn't a valid outer for the Mojave boundary relation - the Sierra crest is quite a ways away anyways
* and the new Mojave looks like a duplicate (same wikidata/etc) of the existing Mojave relation

mountain range tagging is fairly nacent, and inconsistent. take a look at other examples around the US (and world) https://overpass-turbo.eu/s/2fXO for ideas. there has been a somewhat recent push to revive type=multilinestring.

anyways, hope this didn't come off as too abrasive. it's something that is useful just a bit complicated to complete.