Single Player Network Game is a set of Lua, physics, and shapes to simulate a network game using bots. The lua script automatically populates maps with the bot monsters, and the shapes and physics make them look and act like players in a multiplayer game. Note that this only works on netmaps that don't have embedded physics (this is the vast majority of netmaps). There are many configurable settings you can tweak to get just the multiplayer experience you're looking for.
This project is based on RadBurn's Marathon Conflict mod, and wouldn't exist without the work he put in to create the shapes and the original set of physics. I've included the unmodified Conflict shapes in this download to simplify the setup process, but RadBurn did all of the work for that. I have tweaked the physics a bit from the original conflict physics, mostly to make the bots act more like real players in a network game.
If you're just wanting to be able to revive in a single player game without reloading the map/saved game, then there's also a script for that that doesn't have any of the bot stuff.
Adminn said he'd make this script, but it's been literally forever and he hasn't done it.
(Requires Alephone v1.4)
Slight physics modifications. Addition of BRUTAL option for more gore.