Thanks to Endless Details for this info! To run coilovers, you don't have to modify anything on the car per se.....you just need to add a sleeve up front where the strut mounts into the knuckle/hub carrier. The sleeve can be removed in order to reinstall the stock struts at lease return.
The rears just bolt up as usual.
There are X1 specific kits from KW (both V1 and V3 varieties), but they're only sold to the German market as far as I know. I'm currently trying to get my hands on a set through my usual guy here in Calgary. If that doesn't work, I'll try and hit up some of my contacts back in the UK.