There may be something 'out there', but, not here in Ulysses world.
I can say, from what I remember of my first days of Lua (and Gmod's version of it), that this would be a good learning case.
Different ways to do it, but basically, use player spawn hook, count players, add or remove matching bots, add to teams.
There's probably specific teams you may want to move bots to.
Do you know lua at all? Any other scripting languages?
We're not the type to do it outright for those here much, but love helping someone if they have basic attempts.
(If you have one, could move this to dev corner section of the forum)