From reading your post it appears you are a 200GT/500ITC Master And you want to upgrade to 1600GT 3000ITC Correct?
It sounds to me like you are confusing the GT ITC differences and want to blend it all together (to your advantage)
To step up from 200 to go higher tonnage you have to choose whether you want a 500GT license, or a 1600GT (leave off the ITC for now)
You qualify for the 500GT now. You need more time on vessels over 100 GT to go for the 1600GT. I believe you don’t need time as master of vessels over 100 ton though, just time spent while holding the license on vessels over 100 GT. The difference is time spent ON the license, versus just holding the license as a deckhand.
You mention the ‘proposed regulations.’ They are NOT in force yet if they are ‘proposed’ You can’t make the USCG accept this when the proposed rules are not yet in place.