Yes there is better kit out there and has been for many years - the present military SAR has that capability and it will be lost come SARH.
'Pretty good' at mapping the coast just isn't good enough and, having seen the radar in action on the 139 and its limited field of view, you are poorly placed to manoeuvre with any sort of realistic clearances.
The weather radar may be adequate for a straight line let down in uncongested waters to a big target but for anything more complex it is simply unsafe.
You don't say how big a boat you would let down to 0.25 nm but I suspect it is not a small fishing vessel or lifeboat.
Will your weather radar pick up a windfarm survey anemometer mast? They are all over the place.
When it is your life on the line would you rather have the radar that can see dolphins and water breaking over sandbars (so it will definitely see anything nasty you might bump into) - or would you rather have a limited arc radar only designed to see bad weather?
If you need to get closer, you probably shouldn't be there.
that is exactly the kind of remark that allows bean counters to reduce capability that might actually save lives. I, like lots of others, have had to get closer than 0.25nm both to vessels and the coast on jobs and we would not have been able to complete the mission if all we had was a crappy weather radar.