I don't know if this has come up often, but of all the aftermarket suspension systems, using air suspension most easily allows you to adjust ride height.
The whole topic of air suspension (different types of springs, spring rates, compressors, etc) is a bit beyond a simple discussion group post, so I thought I'd do it in some pics.
The relevance to aero is that changing ride height influences both drag and lift/downforce, and air suspension allows easy adjustment, both 'on the fly' and statically. It also means you can maintain a constant ride height front and rear, irrespective of load.
So, on my Gen 1 Honda Insight...
Front struts (note rolling lobe air springs - not donuts):
Rear air springs (again rolling lobe):
Compressor and tank (normally hidden behind bumper):
Valves:
Front height sensor:
Rear height sensor:
Controller (Adaptronic e1280s engine management ECU with custom program):
Gauge screen on controller software (used only during set-up):
The controller automatically maintains correct ride height, irrespective of load. It also progressively lowers the car at speeds over 80 km/h (50 mph) and then when I slow down to 80 km/h, it pumps up very fast (because I don't want to hit a local floodway crossing at ultra low ride height).
I also have a manual driver over-ride for height control, and display the front-left, front-right and rear ride heights on my dash.
It was a lot of work to do all the modifications but I literally haven't touched it now in years.