The HDMI port on the Nucleus One is just for audio out (video is only for the RoonOS admin interface), so in the case of the OP it is not a viable replacement as he is already running Roon core on another device and he would need another device to convert HDMI audio to analog and or digital coax to replace what the MC200 as a Roon endpoint.

A Wiim Pro would be a more suitable replacement for the MC200 in this scenario.

www.cmbintegrations.com
One step from the Presidency
#1 Trinnov Altitude 32-8-16, 271, 8000XE, 7200SEHC, 7200.2, Seaton F18, JL Fathom F113, Revel w990's, Kef R7, ATI 528 Amp, JVC RS4100K, SI screen. Roon Nucleus+, Eno AG, Eno M link, 218.
#2 Mark Levinson No5105, Ayre VX8 and CX8, Vandersteen Treo CT, Preamp varies.
#3 Meridian Ellipse