Why did you only listen to them for 10 minutes?
I agree with your ideas on how to further improve the idea. I have thought a lot about it too, and where to you can take it! But sadly the market is not big enough yet for the wide-ranging possibilities you want to offer.
However, this part is not true:
I have talked with Marco about how they create the SD and it's a two-piece set. However, the nozzle is one piece with the bigger half, it just hasn't been polished so the tips fit better and don't slip off the polished surface. You can look closely and see where the two parts come together. It's pretty much in the half of the large body. So the criticism that follows about the stem coming off has no justification.
If you had talked with Marco, you could have also answered this question:
The impressions are from their customers who got customs done, obviously. So the market is actual on-stage performers. My guess is most are 25-40 years old and work in Germany. I think most customers from In Ear are Jazz musicians, so that gives a hint to ethnicity. They do show pictures from quite a lot female vocalists on their Facebook page.