I think that, in the quest for a cheaper laptop, people won't care much that the product description isn't a grammatically perfect rendering of their local Norwegian subdialect. In fact, I bet a site that mandated English (I know, shudder all you want, but it's true) as the language for sellers would mop up here. Everybody 40 and younger (AKA "your target market") speaks/reads English flawlessly.
Taxes and regulations? Big problem. Totally agree with you. This is probably what's kept Amazon such a bit player in Europe.
Cultural and linguistic differences? Not a major issue.
Most people in Europe use Gmail, right? So they must already have figured out this stuff.
The implication of a consultancy company is that their work is done ad-hoc and in a one-off fashion, requiring lots of work from the company which stupidly only scales with the number of employees.
Software that successfully automated away the most toilsome parts of the job, allowing a handful of people to support intra-EU between any of the 28 member countries would do quite well.
One aspect of the problem is taxes and regulations, which for the most part has to be addressed politically. The different jurisdictions are a cause for friction, too.
The even more significant barrier however is the linguistic and cultural one. It's not sufficient to just translate a say English language website to French in order to start selling in France (and providing proper idiomatic translations for each of the main EU languages is difficult enough). There are cultural differences right down to which website designs are popular in any given EU country at a time. You often can tell where a website is 'located' just by looking at its design.