Hey @Feugy, apologize for the late response and thanks for your explanation.
Even though we strongly prefer this to be in the melodie namespace than chromium as stated in The mpris interface, we have done some research and tests and decided to grant the declaration as you requested (thanks @alexmurray). This is now live.
We still consider the ideal solution is to have the upstream platform making this configurable/customized instead, allowing to have several electron music apps being used at the same time.
Thanks!