This isn't FM2016 mate. You can't just dump six players in one go and expect to buy three better ones with the proceeds at a time that suits you. You might raise £20m by selling Mirallas, McGeady and Naismith - in a good window you might even get £25m - but you want to immediately sign a new starting LW and competition for Rom? Good luck with that.
Mirallas is worth more to us than the money his sale would raise. He can play on the left or the right, is a viable option as a striker (arguably the best finisher at the club), and is younger than Kone so we can expect him to play for longer. He has a track record for assists and goals, and was delivering these when Kone was doing absolutely nothing. It makes far more sense to keep him so that we can use him when one or more of Kone or Deulofeu lose their form, or suffer an injury, than it does to sell him simply because he isn't currently starting. If we are going to dispense with Pienaar and McGeady (and I hope you are right on that) then we can't let Mirallas go too without leaving us a little light when it comes to attacking depth - because he and Kone are our only backups for Lukaku, and Kone's currently starting games.