I do like the notion that Salamander is as much a pawn as Elspeth and Cassy are in the scheme of things, but I dislike the notion that Salamander could plead that s/he was only following orders which made it "ok" to kill (we know Salamander attacks ships) and sell countless innocent people into slavery and who knows what else. It seems very...Nazi.
Aside from that I only have one real problem with the possibility of Salamander being either Saresh or Jakoby's bondmate; we don't
really know them. I don't know why in my head I have it that all major players/characters need to be known, other than it makes their identity being revealed - after such secrecy - have more impact.
Aside: do you want this theory published to the Theories archive, by any chance? The only Salamander theories there at the current focus on the Druid, the Gatekeeper and Saresh, not Jakoby's bondmate:
~Link~My theory on the matter
was that it's Henry Druid, but the descriptions in later books don't sound like the old man at all. But, Salamander showed up around the time the Druid's camp was destroyed, and that Salamander has a beautiful woman speak for him - I agree, that sounds like Erin to me.
Alternatively, the beautiful woman could be Saresh, but Ariel coerces her appearance to make her look how she would if she weren't deformed (which may be why she wants to keep him around). She wears the Salamander disguise when Ariel's not around, to hide a) the fact she's a woman (would the Gadfians/Red Landers deal with her if they knew she was?) and b) her deformity, be it for fear of recognition, or shame in it.
The other thing that made me think the Druid was that the Black Ship has beforetime weapons on it (could it be a reclaimed Navy vessel? Maybe they found it on Norseland, in or around the bunker there - long shot, I know) - we know the Druid was always on the hunt for weapons, even (accidentally?) detonating something when they crossed paths with teknoguilders in Farseekers, so I'd figured that after the camp was destroyed, the survivors headed to the coast with what they could take with them, acquired a ship, and continued doing what the Druid always did; hunt down weapons and plot ways to get the upper hand over the Herder Faction (hence the continued association with Ariel). That the Druid would have sold some of his own people into slavery (including his mute daughter) - well, it's callous but not implausible, particularly in order to seal a deal with the Red Landers that gave him the ability to search their regions and beyond for more weapons. In Farseekers he only seems to acknowledge Erin, and we know the Druid gets rid of anything that isn't his version of perfect.
I'm not saying that Salamander him/herself isn't Sadorian in the end (the evidence is all pointing toward that now), but something tells me the Druid himself is also involved - we've not seen him, only some of his people (that he wasn't fond of) as slaves through the connection to Matthew, and had hints of Erin's possible involvement in the slave trade itself. Where is he? If I don't see a dead body, nothing will convince me he's dead.
As for the second null - I'd be interested to hear the Lidge theory. I think it's been toyed with in other random threads, as has the possibility of it being Jes.