Coulson looked really good in the last few games when he was playing left wing IMO and it felt like his natural position to me, although he didn't really look bad at LB either tbf..
I can see Friend staying on but only on greatly reduced terms (I'm assuming he'll be on about £20k a week at the mo, from the Prem days). Wasn't the plan was to play him more as a CB this/last season? he hasn't really got a chance to show us what he's capable of there, and pace shouldn't be an issue if he's good.
On paper Johnson should be fairly easy to replace, but like people have said - he has his moments & he's definitely not the worst player on the pitch.. so I wouldn't see a problem with them keeping him if we could agree a suitable deal. He's versatile & definitely not the worst player on the pitch when he plays.