Pordon my ignorance if I sound odd in my thoughts.
Vridharaja @ Mutharayas - Vridhi - Vridhachalam - old - senior. Was it Mootha arayars becoming Mootharayar and then mutharayar?? In Inscriptions, I dont thing they differentiate between Moo and Mu (nedil and kuril), its context oriented.
Vridhi can be old or senior and hence Mootha, Raja is Arayar.
remember in vengaiyin mainthan, perumbidugu mutharayan is shown as colluding with the pandya king in organising a revolt againt RJC along with the srilankan general keerthi. the close friend of the hero elango who later turns a traitor is also shown from this clan. the pandya king and perumbidugu mutharayan are shown as defeated in battle/captured and being brought to GKC...