Starting on page 170 of his book, Counterpoint: The Polyphonic Vocal Style of the Sixteenth Century, Knud Jeppesen provides modal, imitative, two-part Kyrie's that he wrote himself as examples. Link at google books:

http://tinyurl.com/yzsogks

There is, I believe, a large potential for excellent, small-scale polyphony in sacred music. One needn't see this as an invitation to insipidity. On the contrary. It's the scale that matters, and that provides great opportunities.