I would have thought a twin-track approach would solve the problem: a SHADER OSM for those on the ground and the aircrew overhead, a la TELIC and HERRICK, and the GSM 08 with an "Air Ops Daesh" (or other suitably worded) bar for engineers, RPAS crews and others not in the line of fire. Establishing a differential in risk threshold between OSM and GSM would be useful as it would offer a means of recognising service without distorting the existing system too much; over time Army types would still distinguish themselves with a chest full of OSMs, while remote combatants would acquire only bars to a single GSM ribbon. Accumulating days of GSM-earning service would also unlock the ACSM, which would further recognise the enduring contribution made by many remote combatants.
A slight problem: they just need to finish awarding the contract to mint the GSM 08... only 9 years after its inception...