If you use pak files, the current in-game download system will still download the files individually. Also, I've had a pak subdirectory on the todo list for a while, but I'm not sure if it was ever implemented. I would recommend not putting the map in a pak file, otherwise it won't show up in the map lists, and if it gets changed, it won't be able to be overwritten automatically.
For now the simplest thing to do would be to distribute your map in a zip file that can be extracted directly to the paintball2 directory. Make sure you have appropriate names for your texture directories - something like pball/textures/y00tz or pball/textures/heist.
