First off I don't officially know why they are doing it ..BUT I do know that SFOG has miles of red tape to go through when they want to build a tall attraction due to the nearby airport. They worked for two years just to get Acrophobia approved. Now maybe...just maybe they simplified the process by tearing GASP down and having the highest point of the new coaster occupying the same or nearby space of the GASP. We are pretty sure that the station will be near the looping starship, so the lift could go towards GASP, or then again maybe they have the right to build tall within a certain area if the GASP is removed. If this is the case we can look forward to 180ft or even hyper status. Just my two cents.
IIRC, wasn't Great Gasp up on a hill? Seems to me that if the top of the lift were at the high point of Great Gasp, which according to thrill network was 225', the actual first drop could be even taller if it heads downhill. I think hyper status is more than doable if they're allowed to make the high point the same height as Great Gasp was/is.
I'm not sold on it having a tunnel, nor am I even sure what company will build it. A lot of signs point to B&M, but I think an Intamin pseudo-hyper like Expedition GeForce or Goliath may be a better fit with the constantly-debated 200' cap, plus they are far more twisted than the B&M ones so it would have a better chance of negotiating the track and supports for the Scorcher. But at this point my guess is as good as yours.. and I'll take it.
I am unaware of the particulars to why SFOG may or may not be fond of Intamin. Heck, I don't even know it that's at all true or not. But having seen the footer markings in person with a slew of other well-travelled enthusiasts we all agreed that our best guess was B&M.