[-quote] Advantage of 4 engines. Engine failure on take-off only requires consideration of loss of 25% power compared to 50% loss for 2 engine aircraft. The principle was that this allowed a higher take-off weight. [/quote]
Need numbers to support that argument. The take off weight is a determined at ceritification assuming a single engine failure be it one out of two or one out of 10. You get what you buy. If you want more weight buy a bigger certified two engine or 4 engine aircraft not more engines