Suárez is a good player, don't get me wrong, but every time I've seen him play for Liverpool I have realised how much he should be playing alongside a #9 striker. He does a lot good but his finishing and movement aren't comparable to someone like HiguaÃn, who you see as his alternative. If he were to join, think about him replacing Vucinic instead. He has 6 goals in 20 starts for Liverpool in the league, for example.
Strong defenses are built upon them being a unit which consistently plays with each other. I'm not sure why you'd want to start a rotational system in our current defense, we have Barzagli who is exceeding all expectations, and Chiellini is back to producing some of his best form, performing very well with each other at the moment.
Also, given the needs of this team, I'm not sure why you'd opt to get a CB that would cost a significant amount. There are bigger problems in the squad that need attention.