Please mind your tone, I’m actually trying to help you here and understand the specific problem you have.
Regarding the Impressum: yes, it’s required - by the law. Also, we rarely get contacted by partners who are unable to provide an address - business or personal. So maybe using their home address isn’t such a big deal for most people, as you’d think?
Regarding Shirtee and their shops - it seems that in their Beispielshop-Impressum there is a space for the shop owner’s address: https://www.shirtee.com/de/impressum/?shop=4120
If you’re not obliged to fill it in and yet use the shop… I’d say that’s at least in the grey area.
And basically, I just wanted to know if a shop setup is in fact the best solution for you. There are quite a few use cases where one would do better on the Marketplace and a Showroom - and no Impressum is needed. But it depends on your designs and your usecase, if it would fit on the Marketplace. But from your reply it does sound like you are looking for specifically a shop system setup