DB-ÖBB has announced a Paris-Brussels to Berlin and Vienna via Frankfurt from this December. Early timetables indicate alternating service in days between European Sleeper (who goes via Amsterdam) however plans are to make it daily.
I can only be happy for more night trains in Belgium after having none for decades 😍
There were some rumours but now it is official: https://www.deutschebahn.com/en/presse/press_releases/More-night-trains-more-connections-more-comfort-and-convenience-DB-and-OeBB-expand-cross-border-transport-11320960#
@maartje the German press release has a nice map: https://www.deutschebahn.com/de/presse/pressestart_zentrales_uebersicht/Mehr-Nachtzuege-mehr-Verbindungen-mehr-Komfort-DB-und-OeBB-bauen-grenzueberschreitenden-Verkehr-aus-11320956
Splitting the Paris and Brussels carriages in Mannheim is a bit of a diversion, but as long as the departure and arrival times are alright that doesn't have to matter really.