Face it, breaking canon has happened since episode three of TOS. What canon would you have liked to see broken and why?
I would like to break the notion set early in TOS that somehow the Federation had a long war with the Romulans yet never saw one. Somehow even Spock was surprised to see that Romulans look like Vulcans. I would like to have seen Enterprise take on the Romulan war, but I don't know how they could ever pull it off in a good way without humans or even Vulcans ever seeing a Romulan. At some point you are going to blow up a ship and beam aboard a carcass to study, or overrun a planet, or have some other species gather information, or negotiate a treaty with at least the use of video. But to have the war and never know what Romulans look like?
I would like to break the notion set early in TOS that somehow the Federation had a long war with the Romulans yet never saw one. Somehow even Spock was surprised to see that Romulans look like Vulcans. I would like to have seen Enterprise take on the Romulan war, but I don't know how they could ever pull it off in a good way without humans or even Vulcans ever seeing a Romulan. At some point you are going to blow up a ship and beam aboard a carcass to study, or overrun a planet, or have some other species gather information, or negotiate a treaty with at least the use of video. But to have the war and never know what Romulans look like?