I was afraid that an account made in that way could create conflicts with the administration of the users created centrally with Gosa2
I think that local accounts and central Gosa2 accounts don't create any conflicts with each-other.
By the way, I have written a blog post about guest accounts, many years ago:
It is about Ubuntu, and maybe a bit outdated, so I am not sure whether it is useful for your case.
Regards,
Dashamir