the ability to go straight from A to middle is problematic, usually you want to make sure to shove B in the player's face when they're on their way to mid. this way they will know where to fall back if mid is lost. it makes your map easier to learn and you have only one chance at making a good impression. you'll also need something more elaborate than those corridors. rooms that connect areas to each other are what makes or break a map (especially 5cp) so right now there's not much to go off of.
You should try making the map for yourself to get a feel for it, it would be a perfect challenge for the 72h jam
http://tf2maps.net/threads/tf2maps-presents-the-summer-2016-72hr-tf2jam.28301/ this is where a lot of people like to try new ideas. worst comes to worst, you'll lose a weekend but at least you'll have learned a couple things.
