The Leaf's could RAS but were mainly about trunking bulk fuel. It always surpised me why newer ships like Fort II went and yet Rovers were retained, I came to the conclusion they must have been a useful size. 18k seems an attractive size, increased size and able to comfortable manage a Merlin/hangered. Maybe 4 x 18k & 2 x 37k, but 4 x 37k looks like an early sale as we have seen with a Bay (I actually quite like that when it secured UK jobs, but not South Korean).It only appears so because some of the ships they are replacing have already been retired. Each of the four Leaf class tankers in service until 2008/2009 had a cargo capacity of at least 28,000t vs the 19,000t of MARS FT. Oakleaf's was significantly larger, and this doesn't include the Rovers (which wouldn't add much...).
I see less logistics capacity, not more.
On the jobs front I would like to clarify:
1, Ship building jobs are cheaper to create than most other MOD created jobs. This is not about money to UK industry, (so the £150m in to UK companies is less important as manual jobs outside SE)
2, Are in the toughest locations (easy to create jobs in SE) Plymouth can't even sustain keeping open an airport!!
3, Have the opportunity to "spin the wheel" rebuild capability lost years ago. (18k tonners not 37k but it could lead there if the Government bullied BP a bit)
4, Help to maintain the RN's business case with the UK Public and Government
MARS may not be a big PR disaster as the Labour party was planning anyway and some UK spend has been retained, but it could have been a big PR success. The RN complains the UK is "sea blind" well I look at decision like this and ask what are they doing to stop it?