How about a miniature bridge with a RC Pi filter to the comparator?
Max.

 

We could leave it biased at 2.5 volts then 1/2 wave rectify it to only use the positive peaks.

That's true. No need to involve the ICL7660S in this. Although we'd be left with a 50 hz halfwave, instead of a 100 hz one, the issue would be far from being critical, and a proper value RC filter could smooth things out.

 

This is what I was thinking. If you used a rail to rail op amp one IC would do it.