Alternatives to the Sympathiser in Battlestar Galactica
FFG actually have a variants document posted on the Support Page for BSG: Optional Rules PDF

Whilst the humans do start with slightly reduced resources, it should be noted that this still makes it quite a bit easier for the humans to win. Your Cylons will have to be very good if they're to stand a chance!

Alternatively, you can pick up the Pegasus Expansion which provides a new "You are a Sympathetic Cylon" (that replaces the original Sympathiser loyalty card) and changes up the rules a little to keep things interesting for whomever happens to draw the Sympathiser card.