I think no one ever tried it with the latest and greatest of components.
I would use a turbo head fish pump/filter thing. They have a jet on them and circulate water. I imagine they would be fine for oil too so long as it wasnt that thick, which it probably will not be. You definitely want a flow to the oil, that would greatly speed up heat removal. several gallons of oil has a lot of heat capacity. I would think it would take a lot over 150 watts of continuous power to really heat things up to dangerous levels. You know, they make a Peltier silent cooler for fish tanks. It goes on top of a flow tube from like an under-gravel setup. This would be really going the limit having like a 30 watts of miniature cooling power in an oil system
I still dont get the reasoning behind one of these systems as a long term plan though? I would imagine the oil would dissolve something eventually? I wonder about thermal grease, stickers, tape, glues. I wish I lived somewhere other than new york city and had lots of random empty space to try out such projects.