Different domains for each subdirectory

A friendly hallo to the Kirby community as I write my first post here! After building several websites with Kirby, my first question is now on its way.

What we have, are various subdirectories of projects like:
Every project is client-administrated from one place: domain.com/panel/
The client can add as many projects as he wants (like new project-three etc) via the panel. So far, no problems here.

What we want, is a rewrite/redirect pointing/something from a unique domain like:
project-one.com (to domain.com/projects/project-one)
project-two.com (to domain.com/projects/project-two)
For this, I can setup a simple 301 redirect at my hosting-provider from project-one.com to domain.com/projects/project-one. No problems here either. But we want the visitors have to always stay at project-one.com. Like domain.com/projects/project-one is the root of project-one.com. And domain.com/projects/project-one/about is project-one.com/about.

And the client can setup his own domains by adding new projects. With as little support from a developer like me as possible (like domain-admin, DNS-entries, Kirby-licenses :smiling_face_with_three_hearts: etc).

(How) is something like this can be done? With Kirby or better via our hosting-provider/.htaccess? Because of the link-URL’s of the sub-sites I guess, I have to handle this somehow with Kirby.