The only end workaround for the sea time is you need at least 6 months seatime on a vessel which is OVER 1600GT as AB. Anything else will lead to the tonnage restriction. If that’s the case then the paperwork shuffle’ has succeeded in limiting mariners who are actually operating unlimited tonnage (both GT and DWT) vessels simply because they are a tug and barge.
I looked at this in the ‘90s. My only option would have been to get an inland masters AGT license. But to what end or benefit? I can still operate the current 195GT Tug, 8500GT barge (19000DWT) and earn a living. But the restrictions are SO convoluted it is mind boggling.