I'm passionate person, who has been around AI from a long time [1] but never going in deep enough. Now it's time!

I've been really looking for some way to concentrate on AI coding but couldn't succeeded to find an AI environment I can focus on. I just want to use an AI sandbox environment which would let me have tools like:

• visibility information
• character controller
• able to easily define a level, with obstacles of course
• physics
• collider management
• triggers management
• don't need to be a shiny, eye candy graphical render : this is about pathfinding, tactical reasoning, etc..

I have tried :

• Unreal Dev Kit : while the new release announce is about C++ coding, this is about external tools and will be released in 2013
• Cry Engine : really interesting as AI is presents here but coding with it appears to be an hell: did I got it wrong ?
• Half Life source, C4, Torque, Dx Studio : either quite old, not very useful or costly these imply to dig in documentation (when provided) to code everything, graphics included.
• Unity 3D : the most promising platform. While you also need to create your own environment, there are lot of examples. The disadvantage is, in addition to spend time to have this env. working, is the languages choice : C#, Javascript or Boo. C# is not that hard, but this implies you'll allways have to convert papers (I love those from Lars Linden) books codes, or anything you can have in Aigamedev are most often in C++. This is extra work. I've look at "Simple Path", the very good Arong Greenberg work but no source provided and AngryAnt work.
• AI Sandbox : this seems to be exactly what as AI coder I want to use. I saw some preview but from 2009 we still don't know what it will be about precisely, will it be opensource or free (I strongly doubt), will I be able to buy it? will it really provide me tools I need to focus on AI ?

That being said, what is the best environment to be able to focus on AI coding only, is it even possible?