After scimming through some articles on WW2 and the veitnam war, some old pictures of flamethrowers used during those wars caught my eye. I looked through some wiki pages on those flamethrowers I found their statistics as very interesting if it was put as a weapon for the pyro, especialy as afterburn got nerfed.

My Idea: Liquid/oil based flame thrower:
It should act kind of like a sticky launcher for the pyro, deals large amounts of damage for crowd control and area denial at medium range, but has low ammo and is unreliable at short range. Hopefully it would also take skill to aim and place traps unlike pyros other flame throwers....

Stats:
Shoots flammable oil at the enemy or surroundings (acts like the gas passer), you cannot light the oil while shooting it, NO airblast. M1 to shoot oil, M2 makes pyro light a match and throw it infront of him (has short delay). Flares and whatnot can also ignite the oil. Surroundings which are covered in oil will burn and can ignite enemies.

[-] -50% ammo capacity
[-] no airblast
[-] cannot light oil while shooting
[-] shorter range
[-] oil acts like flame particles but is smaller and moves downwards instead of upwards
[+] 25% increased afterburn damage
[+] afterburn lasts a fixed 10 seconds (if drenched in oil)
[+] pyros drenched in oil also suffer afterburn
[+] enemies ignite (for shorter period) and take damage when walking over areas covered in ignited oil
[+] ignited areas covered in oil burn for 5 seconds
[+] ignited players shot with more oil take minicrit damage

Design of the flame thrower (based on flamethrowers used in Vietnam war):

http://ww2today.com/wp-content/uploads/2015/02/IWO-JIMA-111006.jpg

if this is similar to other of ur ideas, pls note I did not steal this. may be coincidence