If foley had a bit more experience, i would agree with you that his name should be up there. but it is a bit much to throw him in the lions den with so little super rugby experience. he played great though the last few weeks.
So you're discounting Foley based on Super Rugby experience (or lack thereof) but saying that To'omua should be close to the first option?
To'omua might have played about double the Super Rugby games but Foley would have played double the games of To'omua in 2012 and 2013. I don't think you could really count one's experience as being more meaningful than the other. Foley also played a couple of years of 7s for Australia.
Given what happened with Beale, I would be picking JOC (James O'Connor) at 10 against the Lions. I wouldn't be picking To'omua or Foley ahead of him based on playing there this season. I don't think there is any real reason to rank To'omua above Foley though.