With the melee obviously being a flavour gimmick, I'm not sure how to comment on the others.

The gas passer sounds like it could be strong. Assuming it works like a jar secondary, you can toss it at the entrance to a choke, and (assumedly) any enemy that walks in and takes any amount of damage will be ignited. This could be effective as a way to discourage peeking on a flank, probably not too useful at discouraging a combo push. Will have to see damage and size to really comment further.

The dragon's fury sounds like it may be a super-flare primary weapon. Maybe a viable ranged option. I'm assuming here that in order to use this you're going to be giving up your ability to reflect entirely. It being single shot is going to make it punishing to miss, but really I'm not sure what else to say without seeing stats on it. Damage, reload speed, range, projectile speed, and if it ignites/crits on ignited like flamethrower are all going to be important.
I'm hoping to see it work like a flare with much higher base damage, lower speed, and NO crit comboing. That way it can deal damage with falloff, and not have to suffer a low base damage as a result (like the flare gun).

The thermal thruster is obviously intended to be a combo piece with the Dragon's Fury. And realistically, that's going to be where it gets used. However, this will do TONS to bump up the phlogistinator. I'm just going to go out on a limb and assume one of the two will be banned to avoid crit phlog pyro's blast jumping into a group. I don't really see it being used on any "regular" flamethrower that relies on secondary weapons for damage. Will have to see just how effective the blast jump is, because even the damage sounds like it could be strong (again, assuming phlog/fury).