I'm not totally sure, but I think that even with the cheat above, you can only switch to ships that have the "player ship" flag. To fly a cruiser, you'd need to make all the ships playable, and either make a mission that uses it, or use the cheat. The former would be useful for a Star Trek mod. Have little shuttle-pod fighters, but you get to pilot the Enterprise.
And cheating does not kill babies, or puppies, or kittens, or anything else except time. Cheat codes were originally meant as a debugging tool for developers. It's usually kept as something for the player to discover. In Freespace, it's useful for both testing new builds of the SCP, and for testing mods. Cheats are fun to use after you've already beaten the game without cheats, which I already have.