Exactly, Edd has hit the nail on the head here. If you register your bike in your home state, and get a plate for it, then the bike is "registered" forever. If you don't renew the sticker (which means, as you pointed out, getting an inspection, etc.), your plate is not valid for use at home... but your bike is still "registered" at home. And, you still have a plate for it, and an ownership (registration document) for it.

Agreed. You can buy insurance for Europe (the EU countries) for a North American plated bike. That is a fairly simple and relatively inexpensive process, it is well documented here in the forum. There's a sticky thread that explains how to do it in the 'Trip Paperwork' section of the forum. If you want to go into the Balkan countries, you just buy insurance at the border as you enter each country (about €10 to €15 for each country for 2 weeks, except for Macedonia, where it is €50 for 2 weeks).

It is essential that you have this third party liability insurance. You WILL get asked for it at border crossings and at traffic stops.

Once again, Edd has identified the key issue. Once your annual validation sticker from the States expires, just take a hair dryer to it, warm it up, and remove it. Now, you have a plate on the bike, and you have a registration paper to go with it. Don't worry that there may be a matching, dated notation on the registration paper - cops and border officials never look at that. All they are concerned with is that the machine is registered in your name (meaning, not stolen). They are not familiar with North American registration documents, and won't think of looking for an annual registration renewal.

If worst comes to worst and someone does look at the registration document carefully enough to discover that the annual renewal has not been carried out (this is highly unlikely), you can just state that the annual renewal is a 'road tax' in your home state, and you are not using the bike in your home state, hence, no need to renew the road tax. There is an element of truth to that.

I don't recommend that you go so far as to Photoshop (falsify) anything... there is a world of difference between omission of the sticker and omission of the recurrent state-side annual validation, and outright misrepresentation. I've managed OK with omission for quite a few years, but I would never go so far as to falsify things... that's really hanging your ass out to dry.