Quote:
Your open-minded suggestion seems quite valid at the moment, if we take a look at the linguistic evidence:
1. Lots of Germanic loanwords not only in Finnish but in Saami, too, including layers like: Northwest Indo-European, Pre-Germanic, Palaeo-Germanic, Proto-Germanic, Northwest-Germanic, Proto-Nordic...
2. Only few loanwords between Germanic and Baltic (or Slavic), and none preceding the proper Proto-Germanic level of reconstruction (although older loanwords would be more difficult to distinguish from the real inherited cognates).
3. Proto-Finnic and Proto-Saami are found in the Southwestern Finland at the Proto-Germanic era, around 500 BC (since which we also have retained Germanic placenames in Finland); before that Finnic was spoken in the southern side of Gulf of Finland, and Saami somewhere in Karelia. Saami does not spread to Lapland before the Christian Era, and Finnish still a millennium later.
Indeed, we have a solid basis to argue that the Germanic homeland was in Southwestern Finland (maybe already since the Corded Ware Culture).
One counter-argument:
Few proposed Celtic loanwords in Germanic supposedly precede the Grimm's Law, thus representing southwestern contacts already during the Palaeo-Germanic times (~1000-500 BC).
One thing is for sure that the development of the Proto-Germanic language was very complicated, all options are still open.