No worries about forgetting to ask about crediting, honestly. I just love seeing the game-making process, and I'm glad to help you out with this.
Yeah, I think that a flat "X juice per person transformed or tiered up" would be good, rather than it draining off a sector-based juice reserve. However, making the incubators produce cores by slowly consuming juice would also be good. Perhaps there could be a stat somewhere in each sector like "X juice consumed per minute", and that would drain out of your main juice reserve, or maybe just subtract from your overall juice generation rate via reducing the amount collectible after a mission, since that seems more seamless.
Lore-wise, I was assuming the supports would be monitoring transformation progress and adjusting juice flow to where it's needed for the transformation to progress, or helping the transformees relax and focus on the hypnosis, if the transformation process works similarly to how it works in Hypnothicc, or something along those lines to make the transformation progress faster.
If you wanted to keep the "spends juice to TF faster" idea, I think it'd be good to have the sector-based juice meter be for TF only, and you could input juice into it so that TFs in that sector could use it to speed up.