I don't know if this idea was brought up in the past, but would it be possible/practical to make a program that loads individual mods for on the fly testing purposes (such as when you don't want to load up the entire game in order to test an RTE) Maybe a watered down actor viewer as well.

You can use the game to reload an actor's .ini file already. With clever usage of includefiles you can have an entire .rte reload with this method.

Like including the index file in the actor's ini, right?

Well kind of. You have to be weary of sending CC into a loading loop though.

Ah, thank you.

No I don't think it loads any other .ini file but its own when you reload the .ini

It just ignores those for all I know and have seen.