How the hell does an import naturalising lower their value?
Locals, or naturalised players, are always worth more than the same player would be as an import.
There is literally a whole world of imports out there. Australians (and other locals) are much less plentiful.
I think that, typically, a player who naturalises extends their career, and prolongs their bigger pay checks because franchises know that they will not be taking up an import spot for much longer.
Just think of Starling for next season, and long ago Dwayne Nelson for the 36ers. No way would any franchise sign them as imports (Nelson had dropped out of the NBL I believe)?
Cal Bruton, Ricky Grace, Leroy Loggins, Al Green, Scott Fisher and many others have all done this. If a longer term import wants to settle in Australia, they should always naturalise to prolong their career, and retrain or invest their money to secure their future playing career.