dynamic loading?

I dont know if thats the right phrase but... my game design has a referee who plays the role of npcs, tweaks the events in-game, etc. i would very much like to have it possible for the ref to load for instance a bot, script, object or the like during gameplay. if the example bot or model or whatever did not exist in every map, but only on the refs computer, could he load it and have it sent to each players computer? or are elements of maps/levels strictly limited to what was included when the game started? am i making myself understood at all :)?