More teamwork.

There are a lot of ideas on forums about how any class could help his teammates. (I will write any of them later with links to the posts.)
I will use system "Class #X helps class #Y" as "X-Y" for my ideas.

Examples:
4-3: Bottle that broken at the 1st time makes afterburn longer.
6-8: Metal Arrow, that could go through multiple enemies.

/to be continued.../

Project 'TeamFireStress'

This post is about teamwork and Pyro - how his help can help each other.

For example, shields (Demoman's and Sniper's). Imagine that you can ignite your teammates' shields.
Protective shields (as Sniper's ones, on his back) could burn Spies that touched these shields on Fire.
Offensive shields (as Demoman's one, in his left hand) could burn enemy (as Burning arrow) if Demoman touches the enemy by Chargin' Targe.
Or eatable items: Sandvich, Dalokohs, Buffalo Steak Sandvich, Bonk!, Crit-a-Cola (can be eaten/drunk faster); Mad Milk and Jarate (not food) can be recharged faster.
Also, the Sandman's Ball could be ignited too to have additional Afterburn damage. (Or Fire Ball could take sentry's attention for a short time.)

/to be continued.../