There are a lot of different options. You can search the forums for ideas or even use Google images or Craigslist for different options. Mobilechickencoops.com has some coops that are a good starting point. You could extend the wire framed walls and reduce the solid wood walls to lighten the design. You can also add wheels on the front to aid in pulling. These are just an example from a quick search. I've seen everything from a simple frame structure of 2x2s with wire stapled on and a simple lean to roof to chicken tractors built on hay wagons. The design depends on your budget, your needs, and your terrain. A simple 2x2 frame structure won't last long if you need to pull up and down hills.
Now, you've specified 25 hens and 2 roosters. This means laying hens and nesting boxes, likely 5-10 nesting boxes depending on how many hens you want sharing a nesting box. With that many nesting boxes on a mobile structure, you are now adding weight, complexity, and cost. You may want to split the group into 2 boxes with 1 rooster in each.
Also, do you need a walk-in? That's more height that adds weight and cost. You could reduce the height and lengthen the coop to extend the "free range" section.
