I don't know how to accomplish this timer thing- i dont think, its possible on 2k/2k3- the default battle system and the main game screens with the maps, etc. are too much divided as if you could effectively use such basic commands like the timer. As far as i now, default battles cannot be interrupted by common events, too (which otherwise could have been an oppurtinity to use the timer). These are the main reasons why people try to create their own battle systems, the standard bs is really restrictive. :/
To make certain events like game over and so on appear in standard battles, use the 'Turns Elapsed' option in the 'battle event triggers' in the 'monster party' section of your database (names may vary by version used).