I don't know. It's a tough choice, really.
I mean, argument for yes, is that logically that'd mean we'd get more James LaBrie. And there's no such thing as too much James LaBrie; what a talented man. Pleasure to listen to.
On the other hand though, MP's gruff vocals do add a fair bit to DT's sound, and I do love backing vocals. Counterpoint, harmonies, I can't get enough of backing vocals done well. And I can't imagine they'd be gratuitous. There's a good history of bands with very strong backing vocalists - Queen immediately come to mind, or Nightwish more recently and less influentially - and it'd open up a lot of cool paths. They've barely scratched the surface of the potential. Imagine if they wrote more songs like Don't Look Past Me! That'd be wonderful.
DT are very talented, and I'd probably lap it up either way. I think employing less MP vocals would be playing it safe. More MP would be more of a stab in the dark.
Yeah, I'm gonna say more BVs. Progressing rather than regressing. 'citing.