Pod filters are likely to decrease torque through most of the rev range, but if you're willing to accept this, they look cool. Velocity stacks look better if you like rebuilding your crank/topend.
When the T500 won the IOM TT they used the standard airbox cos it worked better than everything else they tried.
Rearsets, I think mounts etc were pretty standard on Suzis throughout the years so you might be able to modify a set.
Definitely keep an oil tank, oil is injected directly into the main bearings. Maybe lawnmower fuel tank if you want to change it. I bought an old Coleman 4M stove yesterday for $10 which has an awesome tank, maybe look out for something like that.