Joining the fray a little late, but here's my one-fiftieth of a dollar's worth of thought.
Regardless of the heat source, you'll still be battling the same problem of reaching and holding the desired cooking temperature as long as your bullet is exposed to the wind. Even on a decent day, the wind can wreak havoc on the bullet’s temperatures due to it not having a great deal of thermal mass to shrug off the effects of the wind.
Lots of us here on the frozen tundra use ours year round. Cold weather cooking does take more fuel for a long cook (I’m guessing 20% more). But, once it’s up to temperature and well protected from the wind, the WSM will cruise along blissfully unaware of the calendar or the temperature outside.
Long suggestion made longer, try rigging up a windbreak of some sort before embarking on a conversion. The break doesn’t have to be elaborate. Large cardboard boxes, simple plywood shelters, even a teepee made from a tarp thrown over a stepladder have been used with success. I'm using a simple V-shaped break made from a scavenged computer desk.
If you do convert without using any kind of windbreak first, chances are you’ll have to overcompensate with your heat source to account for the wind loss to the point that keeping temps low enough and steady in calm or varying wind conditions will likely then become a new problem created by your first solution.
Also, be aware of how you store your fuel, whether you use lump or briquettes. The humidity outside this morning here in Iowa was 60%. I have to store my lump in the garage and when coupled with the moisture from the slush and glop dripping off my truck at night, the coals do absorb some of that. It’s not a lot of extra moisture, but it is enough to require a little extra persuasion to get them going before a cook.
Hope this helps. Good luck with your project if you decide to go ahead with it.
