Tunings whose size is larger than 12, be they regular or truncated,
could cause problems in pieces that rely on enharmony between
pitches separated by a d2. Two pitches are enharmonic if and
only if they are tuned the same. An example of reliance on such
enharmony would be a D
and an E
tied together. Even if such
a rarity were to occur, it could be interesting to use different
tunings for these pitches in order to highlight the meaning of what is
occurring.
In cases where music modulates by a d2 over an extended period of time
(for instance, starting in E major and ending in D major),
it is probably not so important that pitches separated by d2 be
enharmonic. Those listeners who have perfect pitch might be slightly
disturbed by the failure to arrive back where the music started, but,
on the other hand, this could be fun for listeners with perfect pitch:
only they would know that the music seemed to return where it started
but in fact was slightly altered in the process.