Fleming here. "Traditional" music as Fluke describes it isn't really a thing in the mainstream - It was when Laïs were a thing (back in the early-mid nillies), but only thanks to Laïs and it ended as soon as they faded back to obscurity.
(Urban Trad has a very good selection of traditional folk music from this era as well, dating from both before and after their 2003 ESC appearance, defo check that out if you're interested)
If the Romeos are indeed in... which -massive chuckle btw- that would be such a weird, leftfield pick. Schlager as they bring it is indeed the closest to... um... Volksmuziek (lit.: Folk Music, but really Music For The Common Man in practise). Think Sieneke (but less embarrassing). I do not know how internationally viable they are, but they are a VERY recognisable name that could win the televote.
I would be very happy with Grace who has released a few good songs and has a great voice, and likewise wouldn't be opposed to Paulien Slangen (if she's indeed in).
But then again, I missed Peter Van de Veire's radio statement so i have no clue about the accuracy of what is being reported here. Can someone else corroberate that?