Bigglesbutler - I stand to be corrected by a TP but whilst increasing the number of blades will change your rotor solidity ratio, the only way of changing the disc loading is to make the blades longer as it is the swept area of the disc divided by the AUM of the aircraft.
To my knowledge, the S92 doesn't have a downwash problem (certainly not when compared to the Merlin) and by all accounts is a good SAR machine already (despite the range issues) and will be better in the Mk2 whenever that comes out. I believe that Sikorsky are looking at creative ways of increasing the fuel load carried internally without compromising on the workspace in the cabin.
The 139 on the other hand is always going to be hampered by its cabin size and, I gather, is not quite so popular on the front line as had been expected.
The aircraft on the interim contract were assessed for suitability by the MCA's aviation consultant who is a one man band with only one SAR tour in Hong Kong in the 70s on Whirlwinds. Unfortunately, he has also been involved with the SARH IPT and believes the rearcrew involved (experts in their field with honours degrees and MScs) shouldn't even have been allowed to take part in the SARH proceedings, even though they were the guys who actually checked the bidders claims aginst the aircraft specs and found all sorts of factual distortions and misinformation.