MJ, I think after getting on for almost four decade in the business and being required to change form VFR to IFR and back again in Class G, often a number of times on one flight, I know the rules well enough. I think we're talking at crossed purposes, or you don't understand them.
An in-flight visibility of 1500 metres is required for VFR (rules for RW changed about six years or so). If I cannot maintain that required visibility due to a lowering cloud base, I could perhaps descend in an attempt to find better vis, but this will possibly result in busting Rule 5, depending on ground elevation. Or, I turn back, or change to IFR. In which case the 1,000 foot above rule comes into play. You can't just declare IFR and operate in 800 metres visibility instead of the 1500 metres for VFR if you don't comply with the latter.