The problem with adding the charger to a E30 rather than E36 example is of engine age. The lowest you really see as far as miles is in the 120K range on a 15 year old motor. I say it's only a matter of time before that GRM M42 goes kaput. Then you're talking about a $2K rebuild plus $4K for the blower (if you don't install it yourself like most here would do).
The above adds to the ever increasing delemma of the M42. Any way to add power isn't going to be cheap at all, and at that point, even a cheap M52 motor with M3 cams is going to push 220hp and cost WAY less than any M42 option. I'm all for the M42, but once mine goes, I'm going to wave good bye when it gets replaced by a S50 or S52. You figure for any performance rebuilt M42, like Febi's, you're looking at a good $4K once the old motor is out, and the new one is in. You can get a cherry E36 M3 motor for $3500, then figure about $2K in the swap, and you get 210rwhp outta the box for only $1500 more than a new M42.