[AltPluzF4]

This is near identical to the one I made a while ago.
The only difference is, since in some situations this still balances, I prevent it from even seeing the player. To do this, replace your IsAlive detour with one for CBasePlayer *CTeam::GetPlayer(int iIndex)

These sigs are what I got a long time ago, and haven't broken since... so maybe they would work good for you:

"Games"
{
    "tf"
    {
        "Signatures"
        {
            "BalanceTeams"
            {
                "library"    "server"
                "windows"    "\xA1\x2A\x2A\x2A\x2A\x83\xEC\x1C\x55\x33"
                "linux"        "_ZN24CTeamplayRoundBasedRules12BalanceTeamsEb"
            }
            "TeamGetPlayer"
            {
                "library"    "server"
                "windows"    "\x8B\x81\x14\x03\x00\x00\x8B\x4C\x24\x04"
                "linux"        "_ZN5CTeam9GetPlayerEi"
            }
        }
    }
}

Also, in your code, completely irrelevant, but you have bool unknown, that's bRequireSwitcheesToBeDead
So, you may expect, if that's false, then IsAlive method just doesn't work.