There should be a requirement to enter a bot into the tournament. I suggest that a bot must have done 500 fights in the last 30 days to be able to enter. This requirement should exclude attacks from other bots.
Reason: It is possible to make some really powerful bots that will always win the tournament but they will be unplayable. I.e. the armours/weapons will never be able to be replaced. So the bot will just be logged in every month to win the tournament. If there is a requirement of 500 fights per month then these bots armours will eventually break, rendering them useless.