Shotguns

[Exodus]

Would it be possible to have the Phoenix Fire mechanic the project the Breath of Fire ability? This would allow the shotgun to spray in a conic direction, which would make more sense than shooting 9 projectiles in 9 different directions.

No, this is not possible. The phoenix fire ability is quite unflexible. The only parameters you can change, are the allowed targets, projetile speed and graphic, the range, the damage, the intervall and the damage this ability deals overtime. The last value is always set to 0.01 seconds and 0 damage, because as long as a unit has the phoenix fire buff on it, no other phoenix fire targets this unit (this behaviour is used in the Medivac ultimate, with damage set to 0).

the mentioned rebound/gleve weapon would be classified as an special weapons. you'll most likely never find such weapons in bt, as these are especially hard to balance and quite hard to implement.

Curious, would these abilities be hard to implement code-wise or hard in the sense of making them valuable but not overpowered in-game?

Well, MacGuyver already showed us, that it's possible to implement such effects. It's more a question of performance, so it's hard to program this in a way, that it won't cost a lot of performance. This is because you have to use the event 'Unit takes damage'. Each time a unit takes damage from any source, this trigger would be started. Now imagine two players which each two lasers. Just because of those lasers, the trigger would be fired 40 times a second. Now add all the other players with their weapons and all the creeps on the map, which also start this trigger with each of their attacks.

I guess I don't have to say much about the balancing. We all know that it would be difficult and would take a lot of time, but it's possible to make them balanced.