I think that's a great idea brianmquinn,

Any of the controls that were used in the past to reduce contrast of fixed grade paper - soft developers for instance - would be valuable to put to the task for reducing contrast on this fixed grade paper used in camera negatives.

Hate to suggest a possibility: Blue filter. Would waste the panchromatic nature of the paper. But may reduce contrast.

Also suggests other filter possibilities, selecting red/green/yellow filters on camera - not to enhance the contrast of the subject - but deliberately to reduce the contrast. Thinking in contrary to usual practice - that sounds like fun.