Crossan (Sorry, him again) refers to an interesting text in Paul's letters - 1 Corinthians 9:5
Do we not have the right to be accompanied by a believing wife (Lit. sister wife), as do other apostles and the brothers of the Lord and Cephas?
What the heck is a 'sister wife'? Crossan argues that it is a female missionary who travels with a male missionary as if, for the world at large, she is his wife. The purpose of which is to provide protection for a traveling female missionary. Crossan goes on to speculate that when Jesus sent the 70 out in pairs, he sent them out as male and female to enable female ministry, but with male protection in a violent world.
If it were true it would certainly support our previous contention that women played an important part in Paul's ministry.