Welcome to BYC. Where, in general, are you? Climate matters, especially when it comes to housing.
Is this for layers or meaties? And for how many birds?
The original Salatin tractor is specifically designed for the needs of pastured meat birds and doesn't really meet the needs of backyard layers. It's been a good while since I read his book and I *think* he does have a layer variation, but both his tractors are part of a fully-integrated system with other livestock and their size and weight require the availability of powered machinery to move them. 
 
Some homesteaders have, I believe, adapted the Salatin meatie tractor for smaller batches and lighter weight though and had good success with them.
A-frames, are, alas, one of those things that sound great in theory but fall down in practice.
Because they have to be roofed all the way to the ground they're very difficult to ventilate. Because the roof/walls slant, the space at the point where it is too narrow for a chicken to exist comfortably and the spaces at the base of the wall under the slope where a chicken cannot stand are walk are essentially wasted.
For many people a hoop coop, stationary or tractor-style, is the best option for ease of construction and light weight.
Here are some good hoop tractor options: 
https://www.backyardchickens.com/articles/hoop-tractor.69336/
https://www.backyardchickens.com/articles/hoop-coop-brooder-with-roll-up-sides.75720/
https://www.backyardchickens.com/articles/the-biddie-bordello-a-hoop-coop-run-combo.72189/
https://www.backyardchickens.com/articles/permanent-hoop-coop-guide.47818/