I.R., no, I do not think you're missing the point at all and I agree with your premise regarding V2 variation with weight. Nevertheless, I still seek an answer to the "re-stated" question in my last post above. Hope you or someone else here can chime in with answers.
As far as your "who polices" question, the noise certification regs (FAA or ICAO/EASA) specify that the climb is to be at V2+10 to V2+20, applicant's choice. So, if I specify a "lower than gross TO mass", at, say, V2+20 and that turns out to equal the original "max gross TO mass" airspeed of V2+10, I'm OK because there will be no change in sideline noise levels, That is, (V2+10)HW = (V2+20)LW, where HW is "higher weight" and LW is "lower weight". See where I'm coming from?
The only things I'm unsure about are the operational consequences of flying at V2+20 instead of V2+10.
Cheerio,
Tom