more than 15 unit military inside = impossible to capture ! Defense is the easiest way in war, siege are so OP so it is not an issue.

This is where I think Delenda Est has an advantage, in that the capture mechanic is clearly defined and localized.  With capture out of the picture for the vast majority of buildings, you can do things like adding HP to Fortresses, adding special techs that increase that HP further, add more crush resistance, etc. Capture bar limits these possibilities, leaving you with balancing the balance of previously balanced capture system. 

commands.txt   @user1 My lobby name: tesla2402 Opponents name: deivv Closed the server in middle of the rated game.

commands.txt   @user1 My lobby name: tesla2402 Opponents name: Bokluk Closed the server in middle of the rated game.

commands.txt @user1 My lobby name: tesla2402 Opponents name: Natz Closed the server in middle of the rated game.