The default should really be that each word typed in scrivener gets automatically tagged with itself as keyword; not only that would be a safe redundancy to help find that word with the search function, but would also provide an easy way to duplicate whole documents without using copy/paste. This list of keywords would be magical to generate indexes and glossaries, and I am sure others will find multiple new uses for it.
Maybe an optional second tag could also be attached to each word, …for a fee.
… time for my soup!