I have no reason why pirate factions would participate in FW.
If you join a pirate faction: bam, sec status set to -10.0, and you can freely fire at anyone in Empire. In fact, might as well give bounties to Empire NPC vessels.
Conversely, if you are in pirate space, you won't get shot at by NPCs and you get assistance from gate-guns if shot by non-pirate faction pilots.
Why would you want pirate factions to join FW?
1. Get easy access to pirate LP stores?
2. Get lots of people to join pirate factions just for pewpew or isk?
That sounds pretty freaking awesome to me. I think we’d see more people hanging out in CONCORD space then, as that would be the only place that pirate players couldn’t get you.
*shakes fist at CONCORD rats causing GCC if you fly by with -3 sec status*
On further thought, I think the potential for making life suck for hisec players would be too high for such a feature to be implemented. Build a ship that can tank faction rats and you can go blow all the hulks out of a belt.
Now, include a clause that you’re prevented from docking in Hisec at all… suddenly the core hisec systems become safe(r) for mining and missioning, while anti-pirates patrol the border systems and enjoy the pvp opportunities.