Once you do such a thing then that's one more step to global anarchy, regardless of the good intentions behind it. Trouble brews up, isn't sorted, and the countries who are making a better job at getting on and prospering continually get inundated with mass movements from violent areas; those fleeing feeling they need to get away and get a decent safe life rather than find a way to come together and overcome the bad guys. (Granted they may need outside help faced with well financed military groups.)
The correct solution is for the world to find a reason to sort out Somalia, and I'd have thought 25 years of war there might be moral reason enough, but of course human suffering isn't much of an incentive to other nations. Their own solution is to let some other country volunteer to take the hit of suddenly expanding their population, when their country may already be full by any reasonable calculation.
I am no expert in the details of Somalia, but in such places, a 'head in the sand' approach to ongoing conflict benefits no one save for the armament traders and others who spot opportunities for financial benefit in a war torn place.
If Miliband wants to suggest they find gainful employment in a country they have fled to, then maybe he can convince Kenya that they could use a new city the size of Nottingham. Heck they can even use the name if they like. Or maybe call it New Nottingham.