I would propose the following formula. Assuming a player has played in n FIDE rated games during the time period, where n is less than 20, their rating would be calculated as:

Rating = [ n * FIDE + (20 - n) CFC] / 20.

This would give weight to the FIDE rating, while allowing those without the opportunity to play in FIDE events to have their CFC rating count. This would work for both men and women, and avoid arbitrary weightings based on gender, current CFC or FIDE rating, etc.