I suppose that you already know the clever workaround to, manually do scordatura in Finale ?

I do not know of a plug-in for scordatura, sorry.

Indeed it would be nice to have since a plug-in could save you some time.

Perhaps you could pay a third party plug-in developer to write a scordatura plug-in for you.

Could such a tuning be accomplished via scala tuning settings in the Aria player?

Perhaps not:

http://www.huygens-fokker.org/scala/scl_format.html 

I wish I could pay a third party developer to write a scordatura plug-in, but I don't have the money for that. I remember going to a tribute concert at Columbia U with my composition teacher and friend, the great Stefan Wolpe. We were waiting for the hall to empty because Stefan had Parkinson's Disease and it was always easiest for him to walk when he didn't have to worry about bumping into people. As we sat there, Stefan pointed to the person gathering the music from the music stands, saying, "He gets paid. The performers get paid. The janitor who sweeps up the stage after the concert gets paid. Guess who didn't get paid tonight? Me."  (Stefan never had enough money to hire a private nurse, which could have saved his life.)  Tributes are nice, but all composers have to pay their bills. I've experienced much the same thing financially, particularly because I never wanted to become a professor after my academic work was completed. In anticipation of people thinking that this is because I'm an "amateur composer", I offer this one comment about my music: 

I am not personally acquainted with Roger Király, but I have had the opportunity to examine some of his music, and I consider that acquaintance enough.  Almost every day, in my line of work, I see contemporary scores, published and unpublished, from many different countries, by composers of great and small reputation; but very few have impressed me as deeply as his works have.  They strike me as the work of a first-rate musician, erudite in the best sense, deeply concerned with tradition and with its meaningful development at the present time.  They display consummate craftsmanship and a serious, passionate and original mind.  None of these qualities are so common that they can lightly be overlooked. 

Malcolm MacDonald, Managing Editor of the Review of Modern Music TEMPO, London, and author of Schoenberg in The Master Musicians series published by Oxford University Press.

As my daughter and I like to joke, "That and a buck 75 will get me a crappy cup of coffee at Starbucks." (Ans I don't even drink coffee...)

Are you interested primarily in the notation itself or the playback or both?