I've always been a little unhappy with the 'end game' in any battle. If you know that you only need one banner to win, then you will do something silly like sending a single block unit behind enemy lines to take out that one loose enemy block. Bear in mind that leaders do not know in advance that just one particular attack will win a battle. Here is a solution that may give a 'draw' result and may limit the last move suicide attack.
If the current player gains their winning banner, then the opposing player gets just one turn to gain his remaining banners. If they are able to do so in that move, then the battle is a draw. If a player gained the winning banner on a battle-back, they there is no 'follow on' move.