Who's the Final Arbiter on "To double cast, or not..." ?

Quite the hubbub over the casting of the already oh too familiar closeup face of Jean Luc Picard, Starship Captain (Sir Patrick Stewart) in the roles of Claudius AND his brother, the Ghost of King Hamlet. (To read more about the hubbub go to the ShakespeareGeek blog http://blog.shakespearegeek.com/2010/04/double-casting.html )

Hamlet's father returned, as a flesh and blood "ghost" this time, in the recently aired Filmed No Less version of David Tennant's Hamlet. The "Ghost" in this version effectively asks Hamlet to seek revenge on what is now HIS DOUBLE. I didn't know they were twins. Well, you learn something new about Shakespeare from the concept geniuses everyday. But since I tend to be a "word man", someone who tends to care a lot more about what's actually in the text--you know, that "stuff" Shakespeare dreamed up; much like, I guess, concept geniuses dream up "stuff" they care more about--I thought I'd let Shakespeare make the decision for me as to how I feel about the notion of the "twin brothers" he didn't write.

Hamlet to his mom on this issue: 3.4.54-68

Looke heere vpon this Picture, and on this,
The counterfet presentment of two Brothers:
See what a grace was seated on his Brow,
Hyperions curles, the front of Ioue himselfe,
An eye like Mars, to threaten or command
A Station, like the Herald Mercurie
New lighted on a heauen-kissing hill:
A Combination, and a forme indeed,
Where euery God did seeme to set his Seale,
To giue the world assurance of a man.
This was your Husband. Looke you now what followes.
Heere is your Husband, like a Mildew'd eare
Blasting his wholsom breath.[brother-Q2] Haue you eyes?
Could you on this faire Mountaine leaue to feed,
And batten on this Moore? Ha? Haue you eyes?

-- bold emphasis mine--sorry Will, but I thought it might be illustrative--like some of the caps; none of which are mine.

A couple of things I learned first at the academy about textual analysis were 1) the fact that Shakespeare LOVES to employ antithesis (in this case his subject "appears" to be "appearance") and 2) he never repeats himself without a very good reason, looke you. :) JM