in France and Europe, we never heard about any airbag in an e30, and the 318 is is originally equiped with Mtech1 steering wheel
Air bag was available on special order basis, otherwise MTech I was oem streering wheel.
Looks really nice project. You have done great job there

We have here in Europe one advantage over US models is the general lack of accesories on Euro models. For example i don't not have the following "normal US-spec things:
A/C
Sunroof
powersteering
power windows
power trunk lid
power central lock
etc.
I suppose Euro spec cars are quite a lot lighter than their US-spec brothers.
If You are planning to use Megasquirt i suggest you to take a look VEMS
http://www.vems.huIt's quite similar system compared to Megasquirt, it only have a little bit better processor. Lot's of hardware available for it. You can tune it with same Megatune program as megasquirt.
BTW. do you have BMW OEM towing hook in your car? i suppose it can be seen in one of the pictures you post here.
How do you like the MTech-1 steering wheel? Was the conversion pretty straightforward and did removing the airbag cause any difficulties?
I suppose BMW is the same compared to all other Motronic system cars. I have removed airbags from several US spec Porsche 944 Turbos. You just need to remove air bags and after that you need to cut one wire from Motronic box and connect that wire to another wire (don't remeber which wires have to check them out). If you just remove air bags car won't start. That is mainly because motronic gets an impression you have had an accident and air bags has been blown this causes automatically the shut down of the engine and also fuel pump will stop. But it's quite easy thing to by pass this and all electric work can be done in few minutes.
325i motor steering (not sure of the translation) lighter than 318is one but needs to be relieved
Have you checked out 318I flywheel (for our american friends, not US spec wheel)? I suppose it is already what you are looking for.