I wanted to make this post long time ago but I was to lazy, but now when Pyro update is near i would like to share some ideas i have.

First of all i must say its very good idea for Pyro subclass (like demoknight for demoman) with some cooling/freezing ability, it will add some fresh air to this game. I really like this weapon design and i woud love see it in game.

Stats and abilities i suggest will make it supporting weapon.

Stats and abilities:

1. Slowing target on hit - Its ice/cold themed weapon so it should has slowing ability with slow % decreasing with time - for example 15% when hit with "flame" and decreasing with time by 1% per 1sec . With same duration as "afterburn" (10sec)
   
2. X% Damage penalty - its obvious, weapon with ability to slow Enemies would be too powerfull without damage reduction. Number is possible to adjust.
   
3. No airblast - instead of airblast new ability
   
4. Alt-Fire: Water Splash - new ability that - can extinguish Allies, can remove Jarate and Mad Milk status from ally (same as when you just go to water to remove effect), used on enemies make them Wet (same as when someone is leaving water, water drops are visible on you) - so its possible to make good combo with Neon Annihilator and also can reveal Invisible Spy (visible water drops). Ammo usage on alt-fire can be same as stock Flame Thrower or even reduced.
   
5. No random critial hits - not neccesery, depends on other stats (like damage penalty)
   
6. Frostbite - "afterburn" unique for this weapon - time duration same as stock Flame Thrower (10sec) but reduced damage like Degreaser (1 / tick) Afterburn and Frostbite don't stack (like Afterburn from 2 different Flame Throwers), also during Frostbite added slow effect (like i said in first point). Frostbite combined with Flares, Axtinguisher etc. doesnt generate Critical Hits. Taking health pack, healing, Jarate, Mad Milk remove Frostbite effect, water doesnt remove it.
   
7. Doesnt work underwater - obvious.

Items interactions:

1. Jarate - Jarate can remove Frostbite effect from Allies (hot ♥♥♥♥ can melt Frostbite), also Alt-fire of Cryogenator (Water Splash) can remove Jarate effect.
   
2. Mad Milk - Mad Milk can remove frostbite effect from allies (hot milk can remove coldbite), also Alt-fire of Cryogenator (Water Splash) can remove Mad Milk effect.
   
3. Flame Throwers and Flares - Flares shots and Flame Throwers fire (2-3 sec duration) can remove Frostbite effect from Allies. Alt-fire of Cryogenator can remove Afterburn from Allies.
   
4. Spy-cicle - Cryogenator "fire" doesnt melt Spy-cicle. Also Frostbite duration is reduced from 10 to 5 sec and slow is reduced from 15% to 7%.
   
5. Neon Annihilator - good combo with Cryogenator Alt-fire -Water Splash.
   
   
   
   
   PS sorry for poor english, its not my native language