This isn't possible since the CP300 features SCM which Montage doesn't have.  However feasible the idea is, you are best asking for the feature on Ideascale which is a database of requests reviewed every week by the Yamaha R&D team so you will get better traction there.  Maybe first search if the idea has already been floated and upvote of already there.

CP300 was not SCM. CP300 was introduced ln 2006, while the first SCM piano (CP1) was released in 2010. CP300 had tremendous longevity though. It wasn't discontinued until 2022 (although there was a period in between when it was unavailable for a while).

Yamaha does have the CP300's CF3 piano in the current CP88/CP73, it was added in the 1.30 update. I'm surprised it's not in the Montage M. The data list shows that the M has a whole bunch of CF3 waveforms (23 through 69), I wonder if the sound might be in there under another name. Maybe it was the Motif XS/XF "Full Concert Grand" piano which is still in there. (Or that could be a piano that uses the CF3 samples, but not necessarily programmed identically to the CP300.)

Thanks for the correction.  I went to the CP300 spec page and saw SCM not realizing the spec page summarized multiple CP models.