Is it "allowed" ...?
It's written in trio style. If the composer has no registration indications, you have free reign. If the composer does have a registration, you can still do what you want, and tell people who might "sniff" at your hubris that you are playing it in Baroque style. I would still use legato for the cantus and make sure you phrase according to the text.
BTW, in college I went to a harpsichord recital where the artist played Chopin's "Military Polonaise" for an encore! Did it make sense? Of course it didn't. He did it because he liked it, and it did sound rather lovely.
Play what you like and how you like it, Sesqui. If someone is paying you well to play it a certain way, then do it their way.
Oh, I think it's "der Morgenstern"–morning star not morning stone.