Why not make a larger Lynn garage? Like that honkin' big vacant GE lot next to the new Lynn Market Basket, and sell of the existing garage. Or, the cheapskate alternative, buy a chunk of GE's excess parking immediately across the street from the existing garage to store more buses.
Because size isn't the problem, throughput is. At peak when the yard is fairly empty is when the choke gets felt hardest, because that's when the buses going 1A can't get back from Haymarket in time for the next outbound headway. An unusually high number of the spares have to get cannibalized for run-as-directeds so rotations don't get blown, and all of the routes have some degree of greater-than-norm instability on late schedules if something ends up totally hosing the Sumner/Callahan or Ted. More supply doesn't change that, because the pressure point is driving them to using ever more run-as-directeds to plug blown gaps rather than cycling them in as regularly-scheduled headways.
Lynn will get its apportionment of the new +60 'found' fleet expansion buses from yesterday's FCMB item, but it will have comparably lower effect on new service than the other garages getting them. When applying the extras, the T is probably going to stack them more heavily to the downtown routes and Quincy/South Shore over Lynn/North Shore because the wheels can more immediately and demonstrably hit the ground as capacity increasers to good effect. On the North Shore it helps for sure, but the effect is badly muted by the siphon compared to how much more impact these extras can immediately provide elsewhere. Longer term, the "super-campus" garage facilities consolidation plan the agency has more or less settled on and which is just waiting for Baker/Pollack to bat a funding eye at also helps Lynn via the proposed new Wellington 200+ unit 60-footer garage and its subsequent 40-footer load relief on Charlestown. Existence of that build comes with immediate domino effect of outright closing Fellsway and outright relocating all heavy-repair functions out of Lynn to Charlestown (i.e all 'dirty' work except for the barest-essential S&I functions you need in the middle of a service day) to reallocate almost all of the Lynn facility space to 'pure' storage instead of storage + repair. Also a good move, as it densifies Lynn's capacity within the current footprint to same degree as an otherwise outright expansion of the facility would, addressing most of the need to go bigger or search for a new slab of land. But unfortunately that's also barely staying ahead of attrition, so while a nifty efficiency gain and cost reducer it's not going to do a hell of a lot for frequencies because the run-as-directed % is always going to be a higher share of equipment usage in the 4xx district than at any other. And also, bigger is not necessarily better when it's those fringe-most routes out in Beverly, Danvers, Peabody that have the fewest coping strategies available to them for their equipment chain being decimated by congestion all the way in to Haymarket. If anything can be reshuffled to give a 4xx route higher frequencies, it's only going to be the shorter-haul routes that stay in closer range to Lynn netting the spoils because they're less intrinsically vulnerable to the Downtown drain. The limits of the district--and the vexing case of Salem being such a badly underserved hublet of diverging routes from a further-away point of very high density--unfortunately mean that the only real lasting deke for the equipment drain is to build that Fellsway clone at Salem and detach it entirely from Lynn. Which, as above, is shitty facilities ROI cutting the total opposite direction from where they see max cost efficiency and max penetration payoffs from the big garage consolidation plan. Maybe they have to take that hit and do Salem regardless for lack of other options, but it's going to be a turd on the budget if it comes to that.
Salem CAN be wonderfully and efficiently fed out of a Lynn where routes actually turned around at Lynn in 1:1 inbound-outbound balance, so loss-leader garages are a crummy way on-spec of addressing that problem. But you need BLX and the home-station rapid transit transfer to make it happen. No other solution, including the whole universe of RUR frequency hacks which still unfortunately leave a critical disconnect from Wonderland-Maverick, solves it all lock/stock the way the mere existence of that extension does. Daunting expense at all, it's the only option that hits multimodal paydirt and licks the very biggest of the North Shore's transit deficits in one shot.