Just a couple of points...
The azimuth used by Streetly of old was a non standard alignment for whatever reason. Commercial azimuth will deliver a very dull result with Streetly tapes then and now. We have preserved this setting as the bulk of machines had it and we see no reason to change.
Regarding thread sizes, we still use BA as 2500 machines were built using that standard. Metric will run in BA, hence Markus's frames will fit in M400s but BA will tend to bind in metric.
Our new machines will also have BA threads and non standard azimuth as our goal is to maintain the standards applied to the bulk of machines manufactured. We therefore don't have to run two alternatives and our products will suit the vast majority that survive.
Old fashioned or what!
Martin