Just an opinion....
Caleb = Great Rock performer, although is a 1 trick pony to me.....no place in market for that though imo. Not sure anyone wants/would to by that type of album. That said, he is fun to watch perform.
Almost every Heavy Metal Rock band singer could fall into that "One Trick pony" crap..
Most notably.. Bon Scott/Brian Johnson... Hell you could even throw Halford in there since all he does is scream..
.. yet somehow they made it..
Not comparing Caleb to them as he still has a LOT to prove..
If you don't like Heavy Metal singers then just say it, stop hiding behind the "one trick pony" comments..
I think the issue is- is that music still relevant, or just tied to that era. I think Caleb can sing the lights out.. but it definitely all becomes a wash of the same sounding song to me, regardless of what he's singing. Maybe that sound can make a comeback in teh pop charts... or maybe I'm wrong in thinking that it isn't already there?
Those guys you're mentioning aren't in the "terribly relevant" camp these days.
Even though I probably prefer Caleb and Alex to Jena, she seems to be the one who offers the biggest star potential- big voice, comfortable stage presence, and a somewhat unique sound (kinda garbly in teh back of her mouth, which I don't like- but it's distinctive).