You largely make good sense PPF.
Personally, I don't think we're quite as far along this track as is being speculated. I think the likes of Vardy and Mahrez are of interest to major clubs but I doubt any are ready to spend serious money on them given less than twenty matches of evidence that they're the real deal.
Having said that, we have been here before. At the beginning of 2000, we had a couple of highly coveted players and we desperately tried to hold onto them. However, when Liverpool called, Heskey went. Ditto Lennon to Celtic. And they went because they wanted to. We didn't need to sell them or want to. In fact, we fought very hard to retain both and massively increased Lennon's wages to keep him for a few extra months. But in the end, they went seeking glory and more money and got both.
The Southampton model is not one to emulate in my opinion. It must be soul destroying to see a constant stream of players head for the exit as soon as they can. Their luck will run out soon enough and they'll be the wealthiest club in the Championship within two to three years.
If we attempt to persuade the likes of Vardy and Mahrez to stay when a genuinely big club comes along, we could well end up suffering. The increase in wages for one or two players way beyond the wages of the rest will end up causing issues and we either overpay the whole group or the spirit will deteriorate anyway.
What we should be doing is announcing plans to extend the stadium and overtly express ambitious medium to long term targets. We should then make sure that we do something impressive in the transfer market at every opportunity and just try to ride this wave for as long as possible.