When you are banked way over... the Load/Force is still vertical. So... fuel/oil will still go to the bottom.
While it is true that most 2-strokes will run in any position... your fuel pickup, and oil injection system are still relying on gravity (vertical) to feed them. If you turned your ski, upside-down... and started it... it wouldn't run for very long. (lack of fuel) The 2-stroke wouldn't be damaged... but the oil and fuel tank would leak out the vent... your battery wouldn't' be happy either.
Also... running a 2-stroke in any position also depends on the carbs. If the engine has a regulator carb... it can feed fuel in any position. But a conventional "Float" carb will not.
On some of these 4-stroke engines, they run a dry sump. (like a modern dirtbike) That way, the engine can still be oiled when on it's side. Since I haven't seen a break down of the ACE engine... I can only assume it has a regular sump. BUT.. since it was designed for the off-road market... it may have an internal dry sump. (that would be very cool) In that case... it should be able to self-oil until the fuel system starved.
In a VERY general case.... you can make a 4-stroke run in any position. You would run a dry sump, and the scavenging pump would have floating ball valves to control the suction. Then your pressure pump would feed from the sump, with either a "Clunk" or double pick up. (this is how aerobatic aircraft keep oiled)
Just as an FYI... Here's a pic of my DRZ. If you look at the frame just below the handlebars... you will see a cap. That's the oil. The top frame tube is the oil tank... and if the bike is on it's side (in a fall) the pressure pump can still get oil, to feed the engine.