I don't know what orifice you pull these analyses from
There are all types of doubles players. There is no mould. Look at the current #1 pairing of Errani/Vinci and the other dominant team of the Williams sisters. None of them are stereotypical doubles players. Ash's game fits in perfectly with elite doubles, as clearly demonstrated by her fantastic achievements to date.
Personally, I'd love to see her play a full year with Casey and try to reach the end of year championships
. That would be an awesome achievement! And there's no reason why she can't be great in both singles and doubles - the doubles top 10 is full of women who are doing great in singles atm: Vinci/Errani, Hlavackova, Hradecka, Petrova, Kirilenko, Vesnina and Makarova.