I only just noticed this thread and thought this may be of interest - our 500 racer origianally had an oil cooler when we first built and ran it, but it was later removed to reduce weight and any possible leakage occurring, with no ill effects. G.B. is not the hottest part of the world, but the bike gets a lot of stick and overheated oil has never been a problem.
On the filter front, we have a remote spin on job, tapped into the feed to the big end, this was necessary for us because the engine would not sit low enough in the Featherbed frame with the oil filter housing at the bottom of the timing cover - so, off it came. I would think it possible to replicate what we have done, without removing the filter housing [to keep the original appearance], but some modifications and plugging of certain oilways would be required.
The pictures should be self explanatory, click on the links below them, if they appear too big by clicking direct on the pictures themselves.
B.W.