I do not understand the question you do me the honour to ask.
I don't get why you'd want such a hook. What would it let you do that you couldn't do normally?
What advantages would it have over just copying out the original string files, altering them as desired then putting them into a mod folder?
You've found the water colour entry in mission parameters? I've used them to make water completely transparent, so I presume there'd be no problem going more opaque if you wanted to.