Use a vote plugin and then exec the HS config after the end.
You can use the console command "dm_load" like this for example :
PHP Code:
char sHsConfig[MAX_CONFIG_SIZE] = "hs_game_mode_name" // use your hs game mode name write in deathmatch.ini
char sCommand[255];
Format(sCommand, sizeof(sCommand), "dm_load \"Game Modes\" \"%s\" respawn", sHsConfig);
ServerCommand(sCommand)
There must be other alternetive, but it is the one I used for my external plugin that loads several dm cfg during a round.