I am talking about a plateau as in not being able to increase weight. However, if you were to keep going at 3x12, you would probably gain some size and granted not much strength. What I do is keep the routine going til I hit a wall like that, then either change the rep range or substitute it with a different excersise.
It is a big problem that a lot of clients that I have trained have had. Same reps+ same weight= no gains. I get some that are really strong with no endurance and vice-versa. You sound like you know more than most people so I won't mess with you too much...
I've never tried it but I'm kinda familiar with cross fit. High rep, high intensity with plenty of explosive lifts and circuit-like training. Which is good for shape, fitness (resistance training in crossfit is great CV too) and decent size. But we are in for different goals, I'm in primarily for strength. Wanting to get into competative weightlifting. Not to mention wanting to get back into rugby next year.
Crossfit and Kettlebells FTW!!! It is aerobic and anaerobic at the same time. I am big and strong enough, it is more about making my wife jealous of the way girls look at me.

1000 cals is getting close to the threshold but it's fine. The only risk and main problem is it really slows up recovery. And my body is going to have trouble storing calories if it is burning more than it uses each day. The difference is I'm hitting the weights regularly instead of just dieting. That upregulates my bodies requirement for the muscle that is there. I'm not going to gain strength or muscle mass right now, but, it'll drastically reduce the speed that my body is trying to get rid of the muscle. As you know, the more muscle mass you have, the higher your calorific requirements are. When you go into a calorific deficite, you're body tries to become more efficient, by burning off excess muscle. If the muscle is being used, it isn't excess.
I tried to eat 1000 calories today and I almost died.

Considering my lifts have actually gone up a bit, but granted slowly, and i've dropped from 270lbs to 241lbs since february. It's working fine. Aiming to get down to the 200lbs range, tho will obviously start going by eye.
I think that when you make gains without proper nutrition, it actually has more to do with psychology than nutrition. I have seen guys bench 325 if you don't put the 3rd 45lb plate on (only 315) but when you put that third plate on they psych out.
I recommend starting with the 16kg. I know it seems light, but it will wear you out.