Doom Legacy has support for bots since a long time ago, and they're very good for deathmatches in maps without lava pits, preferably in small maps. In order to start a game in deathmatch with bots, firstly I go to New Game -> Multiplayer -> Start Server, start the game after configuring it, and lastly I go to the console and type the command "addbot" whenever I want to add a bot to the game. For a match with four players, I type the command three times.
The problem is: I'm always forced to recurr to console for that task. It'd be interesting to allow users to add bots directly from "Start Server" menu, during match configuration. Maybe as a "Bot" option, below "Deathmatch Type", that accepts a numeric value. It defaults to 0.
I've sent a screenshot from the "Start Server" menu in the attachments, in order to demonstrate the instructions above.
I've just implemented this feature. Here's a screenshot showing how it looks in "Start Server" menu:

The "Bots" option accepts values between 0 and 32 (the default being 0). If the value is bigger than zero, then DL will call the commands below for each bot being added:
The "wait" command is needed in order to delay each bot addition in one second. If you remove the wait instruction, sometimes you can get a bug on splitscreen where one of the bots assumes control of player two, making it unplayable for splitscreen deathmatches with bots.
I'm sending a patch that adds a "bots" option. Hope it helps.
Patch w108_39_bot_menu.patch
SVN 1453
The wait command needed was because of a race condition. A better solution had to be found.
The committed code waits until after the other players have grabbed their slots before trying to create bots. Because of other problems, it had to avoid the addbot command entirely.