Thanks for the input guys. Sadly, I'm aware of the typical weak spots mentioned: the supercharger PTO and the disintegrating harmonic balancer. Hopefully I'll have time to address these in my own time. When the supercharger goes, I'll fit an electric water pump. The auxiliary belt side is completely quiet and there is no slop or bouncing belt. The phone does a decent job of isolating the noise source compared to my hearing. It's definitely coming from the transmission side, which doesn't rule out the PTO.
I'm leaning towards the source being the DMF since the noise is directly related to the drive. In the rolling video I'm just moving forward and backward. The metallic scratching noise on top of the rattle would fit the culprit being the clutch assembly.
All will be revealed soon!
Apart from this, I really like this car! The moment I got inside, I thought to myself "this is an old school car". Reminded me of the E36 and E46, probably because this Mini was also designed in the same era. In comparison, the R56 and E91 definitely already had the "newer" car feel. Doesn't surprise me that it's sensitive to the oil level, either. The build quality leaves much to be desired but I think that just adds to the character. I haven't owned any fun car since 2012 what with the 911 being stored on another continent, so I'm really enjoying this.
Question: The first time I've heard of DMF was in the context of 964/993, and the best practice seemed to be replacing it with a solid flywheel + sprung clutch. Most cars nowadays are equipped with a DMF. While there are solid flywheel conversion kits sold by OE companies like Valeo, some people report drivetrain failure which may or may not be related to the new flywheel/clutch behavior. Did it just work better in 911's because of the flat six? Are people using solid flywheel with unspring clutch disc? What's your opinion/experience?