[quote=@Rilla]
I see no issue with it. 

Although it can be changed so that he gains an exact replica of their soul, so they can revive and he still gets the benefits. 
[/quote]

Replicas are fine and could be a fun plot device.

By the way, I underestimated the range of flamethrowers. I'm keeping Evvie's range as is for the battles she's currently in, but twice as long as a flamethrower may need to be decreased or else she's a total beast. Modern ones can go as far as 260 feet according to wikipedia so Evvie can send out fire over 500 feet, more than the effective range of most firearms. I imagine her shooting out a stream of fire like a sniper rifle now.