Too late, it's already a mess. Not only should they revamp the combat system, but everything else. With every new update, devcat seems to forget what was already there before it, and their former use becomes redundant; Just look at what Shadow Missions have done to Dungeons. Even the setting seems to be inconsistent. What's up with Eastern Martial Arts in a European Fantasy world based on Welsh and Celtic Mythology? The closest thing we should have to that are grappling and wrestling moves, those existed long ago in the middle ages. Guns are pushing it, why would giants invent something that needs a stat they themselves are lacking in? They need to tear it down and rebuild it from the ground up. I hate to say it, but they need to cataclysm this bitch.
I really have a pet peeve for the people who say Mabinogi is in a fantasy-medieval setting and leave it at that, denying any further change aside from terribly overused generic fantasy elements.
You know what? Mabinogi is a fantasy life, and it keeps true to its promise, regardless of what some people may say. Real life evolves and changes, and people learn new things and develop better technology. The same happens in Mabinogi, new skills show the progress the 'people' are making in the game, and Alchemy/Guns are a perfect representation of the technology that is being developed.
Granted, all the new content may have caused us to lose sight of our roots, but it's not such a huge problem that would justify resetting all of the progress back to square one.