You may be interested to know that "Disraeli Gears," an album by Cream, is named after Jack Bruce's term for derailleurs. As an engineer, I love them. You need a lateral transfer and a speed change without reversing direction, and you don't have much width available. The Derailleur gives you a whole new path for each ratio, instead of adding a second, power-robbing element. It is also a fairly good use of material, giving a much "stiffer" pedal per pound than a shaft.
I can't remember the last time mine needed attention, but I never haul the bike by car or lay it down.
That said, if you have a trike or a velomobile, you should have a completely re-designed system that could easily include an oil bath, and if cyclists would ever accept a clunky appearance, it would be better there, too. The chain length take-up should be done with larger jockey pulleys arranged horizontally, and the chain guided onto the rear cluster by a simple cage as on the front. It is slack there, and easier to displace. The pulleys can be in a tight-fitting case to keep the chain on even if it is thrown sideways by a trike hitting a bump with one front wheel or odd handling in transit. The take-up case can actually float sideways with the chain, only constrained in other dimensions. The big pulleys are to bend each link through fewer degrees to get through. If the bike will be kept upright, you can put a puddle of oil at the lowest point of the chain and not lose much of it while enjoying great chain life and low friction. The puddle goes onto the chain in use, and then drains back.