Success for now. I created a custom population file with reduced bot count, and experimented with bots. I'm pretty sure bots count as players so, I assume this would work with seven people.
PictureThere parameters were in place before the server started:
mp_allowspectators 0
mp_team_unbalance_limit 0
tf_bot_difficulty 3 (Does not affect MvM bots)
maxplayers 32
sv_visiblemaxplayers 8 (Not really necessary)
sv_lan 1 (So no one would join my server)
mp_autoteambalance 0
After the server began, I typed: tf_bot_add red 7 which added seven bots to red. Although you could only see six on the scoreboard, there will still enough. I played through the first wave, which we could not pass, and I didn't notice any problems. I'll double check with actual players later.
Also: The bots that are on RED, don't move towards the spawn point with robots. You will need to manually warp them there with tf_bot_warp_team_to_me.
what about tf_mvm_min_players or something like that
That is for changing the required number of players to start to wave. I dunno how effective that command is, because I can start the wave by myself.