Um a lot of people. A calliope is another tool that the USF would majorly benefit from (i.e. blob killing arty; priest is great against static stuff but its no substitute for a Katyusha in blob killing). Additionally, if these doctrines lack significant early game punch, they could easily be outmuscled by other doctrines ESPECIALLY in 1v1s.
What will happen is when it comes out everyone will use it for a few weeks then the novelty wears off and actual balance determines how popular the doctrine is.
Exactly, otherwise Soviet and Wehr players would just use IS-2/ Tiger commanders every time. You don't need heavies every game to achieve victory, I don't know why people have the idea stuck in their heads.