The CP33 of the last 20 years has only 32 voices & no sympathetic resonance.  That's low hanging fruit for a synthetic replacement.  The minimum improvement would just capture all of its samples at all loudnesses & play them back through a full 88 voices with simulated resonance. 

Sympathetic resonance is actually pretty hard.  How loud to make it, how many notes to make it, are all unknown without an instrumented instrument.

Improving the damper sounds from pianoteq would be quite difficult.  It needs prior information to use samples.  A synthetic damper could generate a certain loudness for a certain rate of pedal movement.  A sampled damper needs to know the full extent of the pedal movement to pick the right sample.

In the CP33's defense, dampers aren't audible in most music.  They're manely audible in extremely quiet passages.

Nice photo of a CFX.  You can count the number of single strung notes.  The stock soft pedal sound would work for the bottom 8 notes.  The next 5 are double strung.  The upper 75 have 3 strings.