It is fun reading all the wishes, especially having participated in the design of perhaps 15 aircraft. The real issue for us all it to recognize the physics of the situation. Making metal fly is not for the faint of heart, and certainly subject to laws that cant be appealed.
First among them is the recognize that all designs must balance, they cannot have too much of anything, or else they will have too little of something else. A design is like a soccer ball, with a field of pentagonal panels. On each panel we can write an attribute: Excess power, hover ceiling, fuel quantity, passengers, crash load limits, load factor strength, landing sink speed, OEI landing distance, etc, etc. Once we achieve a balance (where the aircraft actually meets its design levels of each attribute) we then want to add a bit more of one (more hover ceiling, for example) pilots have a great deal of difficulty realizing that we have to pull out that particular panel, but allow a few other panels to creep inward and lose some value. If we make the hover ceiling higher, we probably made the engine more powerful, which made it heavier, and eat more fuel, so the range and payload all dropped a bit. The design is balanced when the volume of that soccer ball stayed constant as the various panels are adjusted.
For example, I chuckle when someone decrees that the empty weight must be 50% of the MGW! Nice, but of course, if you want a lighter structure, you want a weaker structure. How weak, and where is it weak? Just let us know and we'll be glad to build to suit!