It's not necessarily about what's technically possible, it's just that BA was deliberately designed as an open pug content, not premade content. They added stabilisers to grind for, to increase your chances of being one of people to get a portal. Doing raid content with randomly thrown together groups has a low chance of success, so they advertised it as very hard content and put a warning in-game when you unlock it. I don't think they expected people to go to the lengths of using external comm tools to premake entire 56-player alliances. I know, it's weird design.

Personally I'm not sure if BA should have been connected to Eureka at all, and it is quite compelling content if it was presented as a standalone large-scale raid with relatively high difficulty. They could do things like this in future but let you DF or premake groups for it. Can still expell you from duty on a wipe and put whatever restrictions they want on it. They could straight up put an Ovni-like large fate in one of the open world field zones which rewards you with an entry token, which you can use to queue up at an npc like you would queue for potd or hoh. Open world just got interesting and people interested in punishing large raids don't need to grind through a whole relic-like series to be able to access it.