Now i get your intention. But to make that work you need a good all spanning formula that calculates team souls difference in real time and gets your bonus depending on that.
This approach will spawn a funneling strat. So others are poor while hard carry (guys who scaling from items really good) is power farming and receiving all benefits, hitting critical mass and winning game alone. No counterplay. So bad design over all.
If we make it tie to player networth, then it removes aspect of comeback. As you cant get more resources in bad situation and therefore comeback, also its gonna be abused by supporting class. They are gonna pick it up and power farm after their carry built their core items.
I dont see how it can work and not be toxic to the game.
Also no one gonna prioritize shooting souls instead of heroes in fight.
Straight money increase gonna only promote power farming as strategy.