The main thing you need is a plan, IMO. If you are going to kayak in the winter in a spot where you can't get to the bank quickly and back to your car in short order, you really need to think about whether the trip is worth the amount of added risk. You can mitigate the risk to some degree with cold water gear, but you still need to consider whether it makes sense or not. It's not a crazy high risk, just higher than normal.
I like lined rain gear that is all nylon or poly. It is "warm while wet" according to literature, but that doesn't mean warm while swimming. If I use that gear, I have to make sure that the likelihood of a long swim is extremely low. What "warm while wet" means to me is that if you get back out of the water pretty quickly, you will be miserable until you dry off and change, but you will probably survive to do that. A swim would end the day. I am okay with that.
Whether or not getting back on your boat and then paddling in is part of the plan is something else you have to decide. How hard is deep water re-entry? Do you have enough support (other boaters you can depend on)? If you can't count on being back aboard paddling quickly, you have to stay really close to shore if you want to keep the risk low.