I think there will be many minutes in the Olympic games where Fowles and Tina Charles are on the floor at the same time. In case you haven't noticed because you don't follow the CT Sun, Tina has developed a very reliable 15-foot jump shot since she turned pro, and she can play the 4 as well as the 5 quite competently. I think those two plus Candace Parker will get the lion's share of minutes at the 4/5 now that Griner is out of the picture.
I would expect to see Dupree or Brunson as the 12th player -- as rebounding forwards to fill the minutes not taken by Fowles / Parker / Charles. While they are not clearly better than Asjha, I think they would get the nod over her. If Geno wants jump shooting as well as defense/rebounding/putbacks from this role, then either Dupree or Asjha would be more promising than Brunson, but if rebounding is the major deciding factor, then it would be Dupree or Brunson. So Dupree is probably the best overall choice.
I think Nneka will be a major contender for the 2016 Olympics, but not 2012. I don't think Jayne Appel will be in the picture.