To be fair Leicester are way ahead of us in terms of development and I would argue they didn't start selling some of their best players until they were well established in this league. In fact, they probably didn't start until they had won the league, were playing in Europe and could potentially attract better than what they were selling.
We need to build the quality in our squad before we start to move our best players on otherwise we'll dick around in mid-table forever before we have a bad season and slip into relegation as with all perennial mid-table teams. We sell Mings now and we won't attract another CB who starts for one of the top 5 international sides in the world. How you can say that Mings is the weak link in the back 5 when the others haven't got one international cap to share between them baffles me. Although that's a bit harsh on Martinez as Argentina is just a shitshow of a national team. He should maybe have one or two.
We should be clever enough to move the players on that have reached their ceilings, however, I don't think that we are in a place yet to do that nor do I think that any of our players have reached their ceilings.