Yeah, I'm of the opinion that no current cannon capable big ships would have been broken by having Linked Batteries. The closest that I can think of to being op is @Reiver's Kath build, but even then I doubt it would have been more than some janky fun. I definitely think the making it small base only is based on the future rather than past ships.
I am very divided on the "Imperial-Only" suggestion. On one hand, I want it for my B-Wings as well as for my Scum Firesprays and Aggressors. But on the other hand, Imps need more faction only upgrades and Linked Batteries could have been a way to give Imp Firesprays a boost up to their Scum brethren. Not a lofty place to be, but then a more universal Firespray fix could have come through, and both versions could have (potentially) been on more even footing.