To add a bit of context, the Swedish-speaking minority differs from other linguistic minorities in Finland in that Swedish, per the Finnish constitution, has equal status to Finnish as a national language. It is by far the most spoken minority language in the country (currently about 5.5%. The second largest minority language, Russian, is spoken by less than 1%). Swedish is a compulsory school subject in Finnish-language schools, while Finnish is compulsory in Swedish-language schools (a state of affairs that is not entirely without controversy).
While the Finland-Swedes are generally concentrated to the coastal regions, they don't form a distinct and separate geographic entity from the rest of Finland. Particularly in urban settings there is little to no segregation. Creating a one-seat constituency on the basis of geography would thus be a bit difficult.

The issue then becomes how to identify someone as a member of a minority. In the case of Finland, your mother tongue (Finnish, Swedish or other) is registered by the government, so you would think it would be fairly easy to define someone as a Finland-Swede. It isn't that clear cut, however; you might or might not identify as a Finland-Swede based on a number of factors (which I'm not going to elaborate on here). Deciding which constituency you're supposed to be voting in might, in other words, be a bit difficult.
The political implications would be interesting. The Swedish People's Party is so dominant in the Swedish-speaking areas (receiving up to a 100% of the votes in some regions) to the point that creating a Swedish-speaking constituency would effectively guarantee them a permanent seat in the parliament, which doesn't strike me as particularly democratic. Then again, it might provide ample motivation for the other parties to start seriously contesting the minority vote.
Furthermore, it doesn't strike me as unlikely that the SPP could retain the seat by forming an alliance with one of the other minor parties, such as the Christian Democrats, who have significant support from Finland-Swedish quarters.
And, it must be mentioned, at least two of Finland's 14 MEPs are Finland-Swedes. One (Henrik Lax) is a member of the aforementioned SPP, while the other (Alexander Stubb) is a member of the conservative National Coalition Party and is a fairly popular politician on the national level. Being a Swedish-speaker is not an impediment for a successful career in Finnish national politics (though a fairly decent command of the Finnish language would of course be required nevertheless).

I'm writing this from my vantage point in Finland, but it should only serve as an example.
A few Spanish MEPs are Basque or Catalan, who seem to able to get themselves elected, though not without difficulty, judging by the results from the 2004 election.
The German-speaking region of Belgium has its own MEP (Mathieu Grosch); representing "only" 71,000 people, it is the lowest amount of people represented by one MEP in the EU. In the Belgian federal parliament, the German-speaking areas are part of the generally Francophone electoral districts. In other words, there are special provisions to ensure Germanophone representation in the EP, but not on the national level.
In Romania, who has a significant Hungarian-speaking minority, three of its current 35 MEPs are of the Hungarian minority party, though all of Romania's current MEPs were appointed by the Romanian Parliament; the first Romanian EP elections will be held on November 25. Additionally, on the national level, minorities recognised by the government are entitled to one seat in the Romanian Chamber of Deputies, the lower house of the Romanian Parliament (the Hungarian minority party holding a sizable number of seats in both the Senate and the Chamber of Deputies).

And what about minorities that transcend borders? The Romani people would be the prime example. Currently, two MEPs from Hungary (Viktória Mohácsi and Lívía Járóka) are Roma, but they're only the second and third Romani MEP to serve (the first being Juan de Dios Ramirez-Heredia of Spain, having served between 1994 - 1999).  And there's millions of Roma living across Europe. The indigenous Sami people that primarily inhabit the northern parts of Finland, Sweden, Norway and Russia have no representation in the EP, and very little representation elsewhere. In fact, Janne Seurujärvi, who was elected to the Finnish parliament in 2007, was the first Sami ever to be elected to the Finnish parliament.
Member nations are free to decide how to create constituencies and conduct elections for the European Parliament, with some restrictions.

All of this brings us to what I hope will be topic of discussion: Is the idea of having special constituencies for minorities at all feasible and/or desirable? Should special arrangements be made to ensure minority representation in the European Parliament? How about creating transnational constituencies? Should the EP be a parliament of the nations or of the peoples?

Of course, given that a mere 30% of the MEPS are female, maybe we're actually in dire need of majority representation...