At first I thought that would be wildly impractical but CO2 goes supercritical at just shy of 90°F and a little over 1kpsi. Those kinds of pressures are pretty well unknown in a substation, but occur all the time in refineries and the like. It's basically just a pressure vessel with a relatively mild heater requirement. Eminently doable. I think we will probably see these deployed in the next few decades. SF6 is an amazing material but really, really horrible as a greenhouse gas.
Super critical c02 is a regular extraction process method for certain molecules! You can find it in a number of laboratory applications. Anyway, yes, doable - essentially for the reasons you mention. But also literally done at the moment, for the general extraction process capabilities of supercrit CO2
Here's a guy playing with a supercritical CO2 pressure vessel on a table (seems a little brave to be shaking something at such high pressures!) https://www.youtube.com/watch?v=2d7RGQMCX24
