VintageSnarker summed up my thoughts on Chenoweth in the opera world - and I would add another big hindrance to her would be the absence of amplification. Battle’s detractors constantly went on about her being inaudible at the Met (Sumi Jo, who has a similar Cheno-y girlishness, has received a lot of this criticism as well) and Chenoweth’s voice sub-stratosphere is not particularly resonant. She would have maybe done some soubrette roles — the -inas and -ettas — but, as VintageSnarker said, she’d either age out of them or attempt to push beyond her fach into more dramatic coloratura rep and probably do some damage. The Der Holle Rache she did on her ill-fated TV show is fun as a party trick/lark, but operetta is ideal for her — Bernstein’s Glitter and Be Gay rather than its antecedent Gounod’s Jewel Song.
O’Hara I do think has more of the goods, and acquitted herself beautifully in The Hours — most critics agreed she and DiDonato walked away with the night, and to bring up someone else mentioned in this thread, I personally wound up wishing Audra had done the Fleming role (even though Clarissa was written for Fleming, making her even more disappointing to me, but I digress). Audra’s “Vieni, t’affretta” from Verdi’s Macbeth in Master Class is really searing, especially given the task of performing Lady Macbeth with vocal precision while also conveying the fear and frustration of being coached/harangued through the aria by Caldwell’s Callas. Not bad for a 25-year-old. Of the names mentioned in this thread, I’d say Audra vocally had most of what it took to go all the way, but has made pretty clear in interviews that trying to fit into the classical world at Juilliard often made her pretty miserable and anxious, so I’ll just have to dream about what she might have made of Eboli in Don Carlo.