To get the air springs out you do not need access from above. Just need to turn the top of the bag 1/4 turn and it releases from the top perch. The airline also is accessible from below.
Curious, why are you switching to steel instead of air? I have 3rd row with air and not had any problem with it in 7 years apart from swapping in a new set of OEM bags a few months after I got the car.

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.