Automatic SiteID Creation at record time?

I’m trying to start getting analytics on a platform which will host thousands of sites, and would like to avoid having to keep two databases of Site IDs in sync; rather, I’d like to configure Piwik to automagically record a “new” Site ID as a real site instead of 400ing.

I’d have sworn that I could do this in Piwik about a year ago, but have no actual evidence at present. is a couple of years old, and mentions that this is an interesting idea (which means that it probably wasn’t possible then).
very strongly suggests that it has never worked, but that there may have been ways to “cheat” it into working.

Is this a feature that is under consideration or development? Or, is there a setting somewhere that I (along with, apparently, several others) am missing?