Whilst still waiting for new brake cables, I decided to tackle the derailleur. It had quite a bit of play in both pivot bolts. Not enough to affect shifting much (I think), but it was a bit annoying. I had another RD-6208 with some minor damage to the cage, so swapped the cages, cleaned it up and put it on the bicycle. The other derailleur ended up in a box for part donors for the future.
No more play on the lower pivot bolt. As for the upper / mounting bolt, I think at some point, perhaps I'll have to follow Suntour school of engineering and perhaps stick a thin shim somewhere and see if that does the trick. Not really crucial, shifting works fine. I've seen some NOS RD-6208's, but definitely outside of the budget.
Both cages off
RD re-assembled with undamaged cage
And back on the bicycle