I know this is somewhat blasphemous but I would have no trouble having it cost an extra 5.00 or something to cover costs it is such an interesting historical ship and something a little different for the game. Having played War at sea I know how much the "big gun" ships attract the attention of the casual fans much easier then other units it would quickly become a favourite I think.
Having it as a special release with some spanish captain and admiral cards and some spanish specific flavour ability cards would be great.
Personally, I would expect to pay more and it would be similar to the Victory and Constitution special edition ships we'll be seeing early in 2015.
As I've suggested on the Anchorage forums doing the Santisima Trinidad as a Kickstarter project might be one way for Ares to go with this product idea?