A lot of the pictures of people from the Basques that I've seen tend to resemble that of Scandinavians. I can imagine Lutheranism and other Protestant movements being popular there more than any other part of Spain. Is it possible that this is the case. I something seems to be so
If you look at the pictures you have here you can see how most of them have Brown hair and darker or olive skin tones. These are not traits that come from Germanic ancestry. I am not saying that one group is better or worse but just simply that your theory does not match the characteristics of Germanic ancestry. Is it possible, sure, anything is possible but highly unlikely. This would be the same if I asked "Is it possible that the Irish are decedents of Native Americans. Possible, sure, likely no.
They've done extensive and very trustworthy studies on linguistics, genetics and cultures. It is a well-known fact that the Basque language is not an Indo-European language, and thus bears no relation to Germanic language and culture. The basques are a separate ethno-linguistic group, completely unrelated to all other European groups.