The premise has promise. (Yes, I just went there
The example confuses me, though. The RAW says explicitly:
A warlock can use any invocation he knows at will,with the following qualifications...
What are you referring to? Now if we're talking about when he can replace invocations known, that's a different kettle of story.
Back to the main topic though. The RAI can be a bit slippery, and there should
be remarkably few cases where this Deontology rule crops up. It's easy to get into a 'rule 0' type of debate if too many instances of this are cited, IMO. Good proposal overall though.