Oh, the big bad mother of them all just occurred to me. I can tag to increase the control roll which will receive the full bonus, even if it doesn't apply to individual attacks. So Ten guys who are "Smoldering" (doesn't even matter if they are enemies or allies) I pull off some of the heat to power the spell, let's go with five of the tags, giving me 10 shifts of power, plus whatever I put into it, let's say 9 and I throw two of those into making it zone-wide. Now I tag the other five aspects and add 10 to my control roll. I roll a 9 (easily done with foci, and maybe a fate point) making this a 17 shift zone-wide attack at 9 shifts to attack, 25 shifts total, all by the book.