well... the citroen idea was from my dad's xantia... it had a little lever next to the handbrake (as a stock, standard factory fit)
4 positions
max - with nearzero suspension travel, for cranking the car up to pop axle stands under it without use of a jack, or clearing mega obstacles offroad
"increased" - where it rode about the same as it might if it was fitted with regular shocks & springs. recommended for "poorly maintained roads and traversing kerbs"

(or, speedbumps)
normal.... which was a bit lower than your average car. not exactly slammed, but lower, suiting it's aston martin lagonda stylings.
and minimum - which would slam it almost til it grated on flat clean tarmac. not entirely sure what the use of that was, apart from a specialist servicing thing, looking like a rudeboy, or getting under very, very low bridges. the handbook warned that the steering wheel had to be in a straight ahead position when you used that option, so i suspect it would rub like a mo'fo on hardly any turn of the wheel! and again, no real travel, hard as nails.
plus a button which would firm up the ride in the middle two positions for a more sporty feel and less roll, though unless you were to really push it (none too easy in a 2-litre 5 door with a 4-speed super-slushbox auto) we were never quite sure which position was "firm/sport" and which was "soft/comfort".
great fun pumping it up and down outside mcdonalds windows though

not exactly a full hydro system, as it was quite slow to respond (and often seemed to do one corner at a time), but the look on the server's face if we came up with it on max, and dropped it to min while they were off finding the last packet of bbq sauce was priceless.
really wonder if it's possible to transplant something like that to a polo....... with a huge cash injection of course (like, a lottery winner's folly type arrangement)... did the system ever make it down to the Saxo, is the question?
that car's probably fit for scrap soon anyway

the intergalactic miles he's put on it being quite unusual for a french motor
mebbe i can give him scrap price and add it to the mega never-gonna-happen project list.