Honestly, all of the options you listed work. I'm guessing that due to the setting, you are going to get much more mileage with a Galvanic Saboteur Ranger though.
If you added a fourth player, I'd say a a Bard or an Inquisitor would be ideal.
Any of those can work well. Also, a combat focused Barbarian 1/ Sorcerer 4/ Dragon Disciple 4/ (EK?) can play a lot like a Bloodrager with far, far more spellcasting power, if you want to have a heavy bruiser with lots of magic.
If you are going to use a Rage class for your martial dip, why not Bloodrager? Then you can get Mad Magic without having to spend a Rage Power on Moment of Clarity -- this let's you cast while in Rage (including the spell).
Bloodrager is also a good choice, but I find things like Mad Magic or Moment of Clarity aren't really all that functionally relevant; once you commit to melee, spellcasting time is very much over. The odds that a character like that will close to melee range, turn on Rage... and then decide that they want to start casting spells is pretty close to zero - and in a situation where attacking with Rage suddenly isn't possible anymore, then they won't miss it if they turn it off.
Well, they all work. I would personally choose the one most different from what I,had played recemtly. But on a tactical level, and not knowing what, or if, the fourth will play, Imwould probably go ranger or bloodrager to grab a few more skills for the group.
