You could weld tabs to the struts... If you are really good at welding. It would hard to do and you would run the risk of damaging the struts. But basically, you are goigng to have to buy new (to you or actually new) sway bars anyway. I would just buy aftermarket sway bars for your car or do it right, by buying either the M3 struts or 92 model struts. I don' think the weight difference would be that great. I wouldn't really trust the weld to hold with the way that I drive or through several auto-x's.
The bilstein sports should last most of forever unless you auto- x your car regularly or otherwise track the car. Most of the people that I know that auto-x their daily drivers (any car not just BMWs) get their Bilstien or Koni struts to last 2-3 seasons. Which is 2-3 years. If you do not put your struts through hell like that, then keep the lifetime warrenty in mind. I don't know anybody that have put Bilsteins on their cars that do not auto-x their car or have had them on their car longer than a couple of years. But I am pretty sure they put a lifetime warrenty for a reason, they wouldn't do it if they were losing money on it.