No, none of the DA ever had spanish voices. None of the Mass Effect games either. You must be thinking of Skyrim which had localized voices in spanish.
As for your original post, I would totally support that idea. I love comparing different language versions and find that it is generally difficult to find out what languages a game has been localized in. Each language group generally only concerns itself with their own language, so it's hard to get an accurate list of localized voices and localized text a game has been localized in (for example, french sites will only give information on the existance or not of a french version, german sites only on german, etc.).
I use OGDB which is not always very accurate but at least gives some information.
So yeah, having all languages as DLC would allow me to find out exactly what languages a game is available in, and compare or even play in another language just to change things up. Sadly, it doesn't seem like there is much of a demand for that. Most only care about the original version (usually english), and even languages getting localized voices, many complain that they would rather have the english voices.
Just for information, game companies that usually have a lot of localized voice overs are Sony Computer Entertainment, Ubisoft, and Microsoft Studios. Series like Uncharted, God of War, Assassins Creed, etc. all benefit from a bunch of localized languages, both in text and voices.