Hello Julien,
If this is just a staging / testing site, you could just ignore that message. That message only states that you will not be able to utilize the versioning service from our site. Everything else will work exactly as it should
If you want, we can set your domain to msc.ellipsa3.com first until you are ready to update the domain, let us know and we'll change this for you.
The reason that we do not allow you to change the domain is because many users have been exploiting this previously. They change their domain hundreds of times themselves
Let me know Julien and Thanks for understanding!