If the question mark over Trident's future could be answered, it would help untangle a difficult issue surrounding Scottish independence, Rusi research analyst Hugh Chalmers said.
"When people start considering options for relocations it's only natural to assume that it would be quite expensive and very difficult and that is certainly the case. But importantly it is not impossible.
"We estimate that essentially the net costs of relocating could actually be £2.5-3.5 billion at 2012 prices, rather than the tens of billions or even £20 billion that has been put forward so far."
But he said it would take a long time, and was unlikely to be completed by a target date of 2020, and a more "natural timeframe" would be linked to the entry of a new generation of nuclear-armed submarines, currently anticipated to start in 2028.
More top news
About 6,500 migrants have been saved off the Libyan coast in one of the largest rescue missions this year.
Amy Sharp, 18, posted the request on a Facebook post appealing for her whereabouts after she escaped from a police station.
The Smile singer was pictured appearing to be carried out of the London carnival - but later tweeted she was fine and "just a lightweight".