Unless you are prepared to build some industrial strength equipment of your own design and then move everyone in the neighborhood away while you experiment with this, I fear you are taking your life in your hands.
Normal pressure cookers add a maximum 15 PSI to achieve a water boiling point of 121 C or 250 F. Autoclaves, used for surgical sterilization, go to 30 PSI. You are talking about going more than twice that.
There is no reason, based on the science of Maillard reaction, to believe that it would not occur at a high enough temperature. The presence of excess water would normally inhibit the process because of temperature reduction, but your "super duper pressure cooker" would keep the temperature at a high enough level to allow the chemical breakdown to occur. You might, in fact, discover that it occurs a bit earlier, as water tends to facilitate many reactions. Caramel making comes to mind as an indicator of what might be achieved, as sugar syrup (OK, most of the water is gone, but in principal) browns when you get in the above 330F-165C degree range.
As to crisping based on quick pressure reduction (perhaps when your device explodes?) That seems less likely as most crisping comes at the loss of water, and you are, in effect, keeping water in contact with your food both in liquid and superheated steam form. It would, most likely, be similar to a braised food surface, than a fried one.
Interesting thought. Please don't try this.
Best Answer
The Maillard reaction begins around 150° C. You do not need that exact temperature. Usually, you don't even want that exact temperature; even baking temperatures usually hover around 175-200° C (350-400° F), and those temperatures are held for 20 minutes or more. Pan-frying is almost always a fast cooking process lasting no longer than 10 minutes.
Thus, almost every cooking oil has a smoke point at or around the ideal temperature. Butter is a bit too low around 121-149° C (250-300° F), but the vast majority of liquid oils - peanut, sunflower, corn, canola, sesame, even EVOO - all have smoke points from 150-260° C (300-500° F).
See Wikipedia's list of smoke points for a fairly complete list. Avoid butter and unrefined flaxseed/safflower/sunflower oil (commercially-bottled oil is almost always refined, except for EVOO).
Of course, this doesn't say anything about cooking time or sticking. When we talk about frying or sautéing in oil (i.e. to get the Maillard reaction going), we usually want a quick sear, and for that you really want to get the pan screaming hot so that you can get a good sear on the outside without doing much to the inside. Clarified butter, coconut oil, or any other of the highly-refined oils are the best for that purpose.
If you're really trying to prolong the cooking time, i.e. pan-frying a chicken breast all the way through, then I guess you'd stick with a lower smoke point oil, such as EVOO or unrefined peanut or sesame.