I'm in my 3rd winter with original battery, never a problem, fires right up, even in -15°f, but I don't have a winch, and don't run lights all the time. not sure how much a winch affects battery life.
Have you considered a lithium battery, they are much smaller for same energy, but from what I understand, you have to get used to getting the electrons flowing with lights before you have full cranking power in cold weather
for extra cranking power, I bet you can fit a small car battery in the underseat storage, an AGM battery does not have to be placed vertical, you can tip them or even lay them on their side