Alright, I'm finally back to update this thread with my current solution. I've lived with the rattle on startup for about 10k miles. Just chalked it up to VANOS rattle due to the check valves being stuck open and oil draining back upon shut down. As you can read in the thread I replaced everything other than VANOS components as I just didn't have time to dig into that when I did the chains and guides and such.

Fast forward to my most recent oil change. To recap I have tried BMW 5W-30, BMW 5W-30 with LM lifter additive, and LM 5W-40. I wouldn't usually buy the BMW 5W-30 but I often get it for free so I use it when I can. So I drained my old oil (looked normal for 5k mile oil) and filled up with BMW 5W-30. I also happened to have a can of the LM MoS2 additive I got for free and thought what the hell I'll throw it in there.

What do you know my startup rattle is gone. Driven about 500 miles it hasn't rattled once. Warm start, cold start, hot start, doesn't matter.

The only thing I could think of is whatever special sauce is in the MoS2 cleaned out some crap from a check valve somewhere and it now holds the oil after the motor is shut down.

Not sure if this would work for anyone else but for a few bucks per can it can't hurt. Let me know your thoughts!