I don't remember if I said your sandbot doesn't compatible with other bots.
Look at this screenshot. HPB_BOT, jk_botti, and Akimbot can join with Sandbot without any problems. At least only Parabot which caused my game couldn't be started. If only the Sandbot's bot_count problem had been solved, I can play Opposing Force with it instead of Parabot
However.....
I just found something interesting. I don't know if Opposing Force multiplayer game can only up to 11 players max or not. But for some reason, if I set the number of bots playing to 3 for each bots, any Sandbot members will be "banished".
Check this screenshot for better explanation. You can see if John is the only Sandbot who is still playing in the map. Another Sandbot who join previously has been kicked because another bot has joined afterwards. There are 11 players in the map (3 HPB_BOT, 3 jk_botti, 3 Akimbot, 1 Sandbot, and of course myself)
Well, what do you think? Do you want to continuing your Sandbot progress as soon as possible?