Airsoft can be seen as Larping with Guns, of course few airsofters would like to admit that or look at it that way. I know there is that stigma with Larping but at my age my thoughts are F-dat. I'm confident and certain about who I am to do what I think is good. There is also the matter of my studies about psychology, behavior economics and gametheory which support the exercise.
The way people wear their costume can be compared to the way mil-simers don their gear. I agree with the Confucian view towards rituals. Ritual arming especially when I can measure all the metrics makes sure all my gear is complete. Having played larp it can be similar, except that the gear is the gear and there is no special bonuses to remember.
The skills I need to hone in milsim and their GURPS equivalent:
Map reading - Land navigation (waaaaay harder than you think and a good compass is expensive)
Pathfinding - Land navigation
Undergrowth Movement - Stealth
Crawling - Stealth with HT
Using Rules of thumb to measure distance - Observation ( how else can you report strategic Intel if you can't measure distances accurately)
Team Maneuver - Soldiering under Formations or a Technique Average skill+0.
Hand Signals - Gestures
Gear Organization and placement - Soldiering OR Hiking. For organizing combat gear use Soldiering, for organizing food and supplies use Hiking.
Fast Draw and Speed Load - Fast Draw and should be a Weapon Technique. I think fast draw should be a technique derived from the weapon.
Anyway, the relation to RPGs is as a GM experimentation and first hand experience are powerful tools in description, narration, and saying what is plausible or probable.