We have two Carbery arks, have had them for over 10 years, and they are as good as the day we bought. Can't speak for other makes, but would expect good quality to do the same.
The carberys come with chains and ground achors (at least ours did), and yes you need to use these to hold them down - not from the wind, they are heavy enough - but to stop pigs moving them. They have no base (see later).
They are easily moved by flipping them upside down, and then they can be dragged - two people can do this on flat ground quite easily - we tow ours behind a quad bike.
I would have a base in winter - but you don't have to spend money buying one. Simply go to any industrial estate and ask for pallets, they will throw them at you! Use the boards from the top of one from one to fill in the gaps on another, dont worry that this gives an uneven surface, with some added straw this will be no problem.
Place you carbery ark in position, peg down, and just put a couple or three pallets in, don't worry that they don't completely fill the inside, your pigs will lie on the boards, and the spaces will be filled in by mud and straw over a few weeks.
This then lets you move the ark, and the pallets to a new location without needing heavy gear.
We have the back vent open all year round, they need to vent moisture in winter, and heat in summer.