Number Notation in key other than C, Roman numerals

[dflat]

...I do imagine they are harder to implement due to the fact that there are more characters needed per chord... e.g., bVII7)

yes sometimes we run out of horizontal space in the measure (beat) for the more complex chord symbols (#9b13 etc.)
(Note: there is our Normal and Small size for chords but this often does not help either!)