Sam,
this is such a long thread and I haven't had enough coffee yet to read the whole thing- so forgive me if my suggestions are anything you tried already.
I'd say, either-
keep Spiro Med EAD (because you seem to enjoy them) as long as humanly possible and pair it up with an Olive G. The Olive G is the single most beautiful G string I have ever had the joy of trying (and I'm already really liking dominant Gs and Eudoxas as well). If only the rest of the set weren't so dull, especially E. (And I don't like mixing for me, but that's another topic).
or- (if you're up for serious addiction and happen to live in an area with rather stable climate)
go for a full set of Eudoxas. That to me is the greatest and most beautiful string to "do it all".
-You'll have pizz sound with all the sustain ever needed, a lot of well-behaved growl without zingyness or boink, and serious fundamental and heft to the note.
-You'll have exceptionally lively, clear and singing arco sound that still is kind of hard to get wrong (even though Belcantos are "easier" meaning more forgiving to scratchy playing and less modulable - is that even a word?). Did I mention the pizzicato feel? They feel really nice under the right hand.
-You'll have about $700 less, as that is what they cost. That's the downside.
Best
Sidecar