Coincidentally, Tim Vandergrift wrote an article in Winemaker magazine called "Kit Yeast Trials" which is about substituting yeast in wine kits. It states this about the characteristics of the yeast they choose (and I quote):
"-rapid onset of fermentation
-speedy fermentation
-thorough fermentation
-flocculation
-low foaming
-the ability of the yeast to cope with pasteurized or concentrated juices"
He goes on to state:
"one side effect of the (pasteurizing) process is that it causes some sugars to bond to other compounds in the juice"
"A yeast incapable of cracking away the sugars from the acids can leave the flavor of unfermented juice which shows up as a sugary or candied taste in the finish"
While he did make some suggestions on where one might begin the selection process, that kind of talk convinced me to leave the yeast alone.
Unlike making wine from grapes or fresh juice, we don't get yeast nutrients in our kits (at least I've never had any) except bentonite, which is a clarifying agent that I understand gives yeast something to hang onto in early stages of kit fermentation.