Don't limit breathability, and don't get complicated at all. Ignoring a possible need to keep things neat, even a pile would work just fine unless you are in a hurry and can't wait until next Spring for results.

Compost can be made year around, not just in the summer, and sunlight, during that process, is not necessary.

A pond liner would not be a good idea because that could limit air exchange, something the bacteria that digest the materials need, and it could hold in too much moisture which could cause anaerobic digestion.

This from the linked article may help some, "Alaska’s short growing season and long, cold winters
cause many skeptics to think successful composting
is not possible. Not so! Even in the depths of winter
compost is being made daily in Fairbanks at the
Golden Heart Waste Water Treatment Plant."

http://www.uaf.edu/files/ces/publications-db/catalog/anr/HGA-01027.pdf

kimmq is kimmsr

That's a very nice and neat looking bin. It does need to drain out the bottom so if you line it, that brown leachate will have to go sideways and find somewhere else to drain. In addition to the lack of air getting to the bottom, which is the only reason to put it up on a pallet in the first place. I would line with chicken wire if anything.

The pallet is going to rot away in a couple years, just be prepared. You'll probably end up making your next bin straight on the ground.

You might consider using one section to put fresh materials in regardless of what they are, just use what you have at the time. When it gets full turn it into the next section and start fresh. That way you always have a pile finishing or ready to use, and a place to put new stuff.

I agree, you don't need a bottom. If you have more than one location to put it, you can pick it up to harvest the finished compost and move it too another place in your yard. The dirt under the compost bin will be great for growing. Air circulation is important.

I recently moved mine to the edge of a garden bed so the compost leachate will soak into the soil where it can do some good.

"I was thinking of
dividing it in 2 to compost fruit."

No! Fruit needs to be layered between dried stuff or it ferments, rots and attracts bears and other vermin.

Well spotted Lazy. I missed that. By all means divide into two but mix up the materials as much as possible. A fruit only bin would be putrid.

If a compost pile has fluid, "leachate", flowing out of it that compost pile is too wet.

kimmq is kimmsr

A poor choice of words on my part.. Mea Culpa.

Moving the compost pile (read that as worm bin) provided the opportunity to host a worm bin right in the soil where I grow my veggies.

The bonus is - I now have the finished compost next to where I will use it. I don't have to haul it any distance.

Next year I can move them (two bins) to the another spot and plant where the bins ("leachate") left their marks (nutrients).

In the real world, sometimes the compost gets 'too wet'. This is why we don't compost in a plastic bin with no holes in the bottom. It doesn't mean the compost is mismanaged, just that we have other things to do than babysit our compost piles constantly. When the weather dries out, the compost dries out. <shrug>