I totally agree with a "best means best" meritocratic approach. It has proven successful in coaching, though often with the risk of losing that successful coach to another place they've called home. (...or their "dream job.")
But there's this constant complaint (not mine) that fans aren't satisfied with word pictures--our fans also want the announcer to reflect their level of excitement in the play-by-play.
So it's an unusual job description:
We want a professional play-by-play person who will then sacrifice his professionalism to become a homer. An "objective homer." But not too objective--at least against certain teams.
I can see where the best way to hire that kind of jackalope is to find a very professional alum, whose head will be professional and whose heart will provide the passion. But it's a tough balancing act!
(And I wonder if becoming that announcer ends your career opportunities to ever go back to being an objective professional again? How many SEC announcers end their careers by retiring? Seems like most.)