A single beacon next to the power pole that covers the entire factory, while I'm not sure the number of modules or the strength would be like for balance since it would be a single beacon out of the way of everything(that you can then build more beacons on the factory floor to boost the machines around it) would make a suggestion of 6 modules that give the base effect of the modules.

might be an idea for an entire separate mod, surface-wide beacons. i would like this.

I double that idea!

It wouldn't necessarily need to be surface-wide; in fact that would be a bad idea if you ended up creating enough Factorissimo buildings to use up all the allocated surfaces, and ended up with two factories on the same surface, because then both of them would get the effects of those surface-wide beacons.

It would work alright to just place a single invisible beacon in the middle of the factory, with a 30x30 (Mk1), 45x45 (Mk2), or 60x60 (Mk3) area of effect, and have the interface for it simply not appear until unlocked with the relevant research, wouldn't it? Heck, give it multiple tiers for extra module slots.