Note that [metro] has a lower limit of 1 ms, so you need to make your own metro-abstraction.
Ah - I had no idea that this was true. I suggested using a metro with a rate of 1/44.1 ms as an alternative to [block~ 1], but I guess there's no way around it...
It seems like the best thing to have for this case would be an extern that just reports the level of the peak sample in each block. Time resolution would be limited to the 64 sample block size, but there's probably not much need for this to be faster, right? And you could always reblock if you need more. Maybe you're looking for a purely vanilla solution to this, but if not, the extern would be quick to make if someone hasn't made it already. Let me know and I'd be happy to do it.
William