Sorry, but it's a bit simplistic just to want more pwerful engines. There are a lot of powerplants out there that will produce more than rated power. Generally, the other important limitation is the power that can be transmitted by the main gearbox, particularly when the power input is assymetric: ie, one engine input no power and the other megawatts of it!
So the answer is to build beefier gearboxes, you say. But hang on! The whole darn airframe just got heavier, so we're back where we started.
On a more optimistic note, if a powerplant may deliver more than rated power in a tight spot this may perhaps be at the cost of an engine and gearbox after the successful forced landing. Still less expensive than crumpling the whole aircraft.
Going back to the original point, and reinforcing what Nick says, when aircraft are certificated for Cat A (or equivalent) the test pilots and engineers will develop the best profiles (capable of being flown by an average pilot) for different take-off and landing circumstances and these will be certificated, subject to the associated and defined WAT limits. Stick to the graphs and the profiles and you should be OK. There are quite a few twins around that can operate to CAT A conditions at MAUW from/into restricted areas using the approved techniques on more days than not, in temperate UK-type climates.