Well, personally I'd try and turn the Corsairs attention to the Hessian. Once they've had their little scuffle, do what Tic said and engage if odds are favourable.
Heh, when I was pretty much forced into allying with the Order in Omicron Delta to defeat a Nomad fleet, I was planning on letting them take the bulk of the fire, defeat the Nomads...then stab the Order in the back and finish 'em off!:lol:
I'd say in roleplay none of these factions should work together, ever.
Corsairs - Red hessians = at war (according to the description), not likely to team up. (Order and LN against nomads is different, since nomads hate humans in general and all humans tend to survive). Corsairs - Bounty hunters = like water and fire. Very, very unlikely to team up. Red Hessians - Bounty Hunters = unlikely. It's lawful and unlawful, the Red Hessians aren't very peacefull, and since they are against traders, it's very likely, said bountyhunter will come for their head some other time, it would be best to dispose of any future threats.