Really... Where are the wheel limitations? You just don't know of any of the wheels available or they actually don't exist? I think most of the e30 forums would disagree with this statement. Sure it might be a little cheaper to grab up some OEM wheels that don't fit properly and slap them on there and run 245s out back which don't fit either but it certainly has boat lots of more traction than 235s on properly fitted wheels right?
What suspension? You can get coilovers to shocks and springs. JUST like a 4 lug car. So again WHAT is the limitation? You could run motons on an e30 with race springs. The amount of lug bolts you have has ZERO bearing on what suspension fits or is possible. Hell Ground Control makes a Track kit for 1400 dollars. So what is the problem here?
What about brakes? Hmmm these would seem to work just find in one of the many 15 or 16" wheels available for the e30 in the correct offset...
5 lugs doesn't give you more traction... I don't know where you came up with that idea... That just doesn't make any sense. How does adding 1 lug per corner give you more traction?
The name calling really isn't necessary. When you get right down to it you do NOT need to do a 5 lug swap. Sure you may have some cheaper options in wheels but the 4x100 has a BOAT load of wheels in varying offsets and some without the proper offset can be made to fit with some proper spacers from H&R with the Trak series. There are suspension options.
Bottom line is you can build a badass car without doing a 5 lug. End of the story.
More than likely you wont' be sheering off wheel bolts so I don't see how 5 lugs is going to stop you from breaking stuff. You may break some axles but there are plenty of e30 guys running the stock stuff out back with some decent power.