Since I haven't used Hammer or somesuch before, I'll try working on philosophy of design. Which is actually covered in Valve's commentary.
1) Every class needs some part of the map to allow them to shine, somewhat.
Whether its sniper battlements, areas just big enough for sentry FoV, height advantages, or others, every class who relies on terrain should at least have 2 or 3 areas where they can say "Wow, this really fits my class". Secondary paths for spies, open areas for snipers, high areas for soldiers and demos, areas where you can get somewhere quickly with a perfect doublejump (Like the spires of Badlands, which are also cool for soldiers): all these are useful.
2) A concept of the map is useful. Why is Reliable Excavation and Demolition fighting Builder's League United here? This can create some interesting elements.
3) Multiple paths. There is no way a single chokepoint should control the whole map. Warpath may seem like this, but it actually has 3 ways to and from the middle point. It's major chokepoint issue is by the last points, which I bet is designed to prevent spies from getting through too easily.
Umm.. that's all I can think of for now.