No it doesn't have to be from outside the EU. I don't know about kits, but for already built planes, it works like this:
We bought our 'new' DA42 through Denmark earlier this year. The rules seem to be that the aircraft has to be 'used'. To be 'used' there are two rules, the plane has to be more than 3 months old and have at least 40 hours on the airframe at the point of sale to you. Ours had 40hours 5 mins on it.
The way it works is that a British Company, closely associated with the Austrian factory buys the plane new. As it is a 'within EU' between companies deal, no VAT changes hand anyway. Then when the plane is 3 months old and approaching 37 hours, you set off to Denmark with the UK salesman. In Denmark, he 'sells' the plane to a Danish company. Again this is a company to company sale and so no VAT actually changes hands. Then the Danish company sells you the plane. VAT is a consumer tax and so when they sell you the plane, they charge VAT... but its a 0% for a secondhand plane, in Denmark. You are then presented with a lovely certificate from the Danish revenue and customs to say that EU VAT has been paid on the plane, albeit at 0%. And this is all done whilst you have breakfast, so by 10.30 am you are ready to fly home.
I will PM you the details of the company to use as I don't think that I can post that here. But they were excellent and will know the answer to your question. They are also very creative so I'm sure they can help.