Beware of definitive opinion...
Reason of change can be multiple so fact is that he has chosen another axe for Romeo because of reason 1 and 2 and 3...
National is not easy to play and we know Mark is struggling playing guitars, leaving the "fender" typed axe mostly for easier "gibson" typed ones (if I get right, despite looking like a Strat the Pensa are technicaly closer to a LP than a Strat).
We also know that the vintage style "O" National have been hugely used over the years and has aged.
But fact is that Mark have chosen to replace it by a quite different sounding guitar whereas he could have looked for something similar as his National if he had wanted to.
So I still wonder why ?