[JimD]

I went and looked at the 135i oil change DIYs and the drain plug appears to be near horizontal as Dack suggests. I am still not sure there is space to rotate a wide plug nor am I sure there is room for it's length. But it might work. If you can install one with the nipple for a piece of clear tubing you can eliminate a cause for spilling oil. It also eliminates the need for tools to drain the oil. The ball valve turns easily with one finger.

The drain plug in at least my 128i (N52) is 17mm. Apparently that is like the N54 but my drain plug is vertical.

Jim