Using Siena to transfer Dzeko or Krasic through would be the perfect way. Most likely better with Krasic as he wants to come to us more, and might be willing to do it. He wouldn't register for Siena and wouldn't play any games. He'd come straight to us the day after signing for them and play for us next season, he wouldn't need to be anywhere near Siena for more than a day.
When we signed Mutu, we had already signed 2 non-eu players from outside Italy that season, so we gave money to Livorno who signed him in January, and we bought him straight of them and he played for us. He didn't need to play for Livorno, we just used them to get past the non-eu rule. This would be exactly the same case.
So we'd get Krasic and Dzeko and problem solved.