I'm not saying I'd do a better job than them, and for the most part I think they both do a good job, but we need some fresh blood in the moderation department. Both hilariousandco and mprep have been mods during my entire 7+ years on the forum. I can't help but think that, with the exception of dealing with giveaways, moderation is loosening to the point where it is encouraging a new wave of spammers on the forum.
A new global mod wouldn't be such a bad idea as they could pick up slack in other areas without a moderator, like P&S. I really can't think of a downside to adding new blood to the administration... things seem a bit stale up there.
Structurally speaking, I believe what you are describing are two different concepts, rather than an inter-connected one:
(1) A new global mod to pick up forum-wide moderation slack (2) A local mod for P&S and other sections that require moderation
A global mod shouldn't be wasting their time moderating non-moderated sections, as I am certain there are more than enough mod reports to get through, especially from those types of sections.
Furthermore don't expect a new global mod to be picking up slack elsewhere from badly moderated sections, unless you want a global mod to become quickly exhausted.
I like the ideas of what you are suggesting to improve forum moderation, but to me they are two distinctly separate proposals it seems. Just my two satoshis.