The problem is...the closer you embed in Downtown, the more infrastructure dependencies you incur. Including things like "how big a water main to flush the toilets that far out to the fringes of the Seaport?" Locating near the CBD makes it less likely that the thing can be full private-financed because the dependencies and complexities get greater. Now, it's one thing if there's some broad-based transpo improvements that slug their ROI 365 days a year...it's quite another for the utilities on a usage case where 300 toilets are all being simul-flushed at the start of halftime. You're simply not going to get utility stressors like that with literally any other land usage case *but* a stadium. So why kill ourselves over that???Perhaps a downtown location with severe height restrictions due to Logan. There are locations like that out in the far Seaport.
I'd support a full-private stadium in the CBD, too, if somebody could come up with one. I just *extremely* doubt anyone's going to come up with one, because of the scaling challenges. So we're back to existentials re: why does it have to be full-embedded urban in the first place and what's so goddamn objectionable about the suburbs on-spec?