Well, Ive never locked the Vanos myself but here is what I think is done for an E36 M3 engine:
For single vanos, the intake cam has the vanos gears removed. Then you remove the camgears and lock the cams in a fixed position.
I believe the way to drive the cams is with two M3 3.0L exhaust cam sprockets, using a 3.0L cam carrier. Standard cams should be locked at 108 and 110 degrees. There's an end cover available stateside, or two custom made plates are required. (easy to CNC)
In NA form peak power is unaffected but low end torque suffers a lot apparently...in Fi form....I dont believe it will be such a problem at all.
A standalone is of course required with the Vanos delete..
This pics show a few blanking plate setups....
if anyone else can add any more to this topic that would be excellent