whilst the LH cone is still in one piece, it shows a more extensive wear mark than it should do. This strongly indicates that the bearings were not set correctly.
The correct setting is a little free play that just disappears as the QR is tightened. If there is no free play your bearings will be merrily grinding themselves to atoms, once the QR is tight.
The damage to the RH bearing is partly due to (salty winter) water ingress and partly due to the bearing loadings, which are higher on the DS anyway, even if the hub adjustment is correct. If the (usual type of) grease becomes contaminated with water, wear rates are likely to be x10 higher than normal.
If that were my hub I probably wouldn't bother to replace the freehub body; it doesn't look that bad, and (from the cup, the balls and the cone) the cup has the least effect on the running of the hub. Also, if the bearings inside the freewheel mechanism are play-free but a bit rough, this has zero effect on the normal running of the hub. [In fact I'd sooner have a freewheel with rough bearings and no play than the usual arrangement of smooth bearings and a little free play.]
From the pictures it is even possible that the RH bearing seal wasn't even working at all, because it appears to be set down into the freewheel body more than normal.
If you want the whole affair to work properly and last a long time, I'd suggest three things
1) New RH cone and ball bearings, please
2) if you have not done so already, learn to adjust the hub bearings correctly. (If correctly adjusted and lubricated, even cheap hubs can look better than your LH cone after 20K miles plus....)
3) Use a semi-fluid grease which contains corrosion inhibitors and solid lubricants, not the usual rubbish (in the context of UK weather) grease that shimano use.
You can pretty much put as much SFG into the hub as you want; it will get into the freewheel mechanism and (if it is the right grade) it won't interfere with pawl engagement. The right SFG will (unlike a standard #2 grade grease) keep seal lips wetted and therefore functional. Seals in hubs often fail because the lips are not wetted with lube after a while.
SFG is also a good choice because most of it will stay inside the hub, even if the seals are not quite perfect. [If the seals are perfect, you can run a shimano freehub in gear oil if you want, but this possibility is rare these days because the RH seal is meant to 'seal' against the lockring screw thread on the seal OD. Oil will always leak through the gap.]
I make my own SFG for this purpose but a suitable off-the-shelf version is the kind of SFG that goes into land rover front swivels. The only bad things about this lube are
a) it stinks
b) if you get any on your clothes, they are ruined.
cheers