Winguru - you said, "I'll ask around".
You have. There are plenty of people here who have done (and still do) what you are asking about. The advice you have been given is very good. Not to mention free.
At the moment neither you, nor your mate, have the knowledge necessary to do what you want to do. Engage a professional (get decent recommendations) or your mate may lose a serious amount of money.
1. You need a trust company to own (that is, register with the FAA) an N reg aircraft. Trust me - I do it.
2. Insurance is generally purchased in the area of aircraft residency. For you that would be Europe. No American insurer will touch you at any sensible price. An annual policy, for Europe, can be bought with a ferry/purchase add on.
3. Your mate needs an FAA standalone PPL with complex and high performance signoffs to fly a Meridian. Once he has that he can do the turbine and IR training - there are quite a few specialist "schools" in the US that can do that in his aircraft. Google is your friend and Piper should be able to help identify good ones. Don't discount sim training for the initial turbine stuff; it's cheaper and much better for emergency drills. Once you can manage the turbine then you can add the instruments. Or vice versa if he does an IR in a piston first.
4. Buying an N reg aircraft without the proper procedures will leave your mate with a very expensive metal statue and more expense to get it flying again. When a non-qualifying person/organisation buys an N reg aircraft the paperwork filed with the FAA for change of ownership will trigger an automatic de-registration. If it flies after that you are illegal and uninsured. Getting back on the register may not be cheap.
5. You need insurance. No school worth the name will instruct without adequate insurance and a trans-atlantic ferry flight needs specific insurance provisions. Not to mention EC785/2004 once you hit the EU boundary.
6. FAA flight training does not have to happen in the 48 contiguous. If you will be flying this side of the pond then some of your training needs to be here. Procedures are VERY different.
7. Don't forget the import. The letters on the side have no bearing on the VAT status of aircraft flying in Europe. You've missed the cutoff for the "cheap" Danish import route.
8. Changing the letter on the side of an aircraft can be a very long, and expensive, process. You need to have the maintenance organisation in place before you buy to make sure that you are not buying something stupid. See point 4 for possible outcome. Even if it goes well the aircraft will be grounded for the duration - are you sure that you need to change?