Who will be paying for the techs to design and implement this new operating system, write the basic software to make it interactive and then design software applications for it to run on top of the operating system, let alone "support" the operating system once it launches to the general public to answer the hundreds of emails and phone calls that will come in?
Example: It took the combined efforts of Microsoft and IBM two years to produce the operating system called OS/2. These are two highly staffed companies with very deep pockets, mind you... and it took two whole years just to have a text based operating system.
http://en.wikipedia.org/wiki/OS/2IBM and Microsoft split company back in 1990. The next Microsoft release was Windows '95. You can likely do the math as to how long that took, with dozens of highly trained (so they say) technicians designing hundreds of smaller applications which when combined, became the operating system.
My guess is that you're not actually after a full blow OS, but it sounds more like you're interested in a "UE" (User Environment) which is generally more user-friendly than the typical Linux desktop, but less costly than one from Microsoft. That's not impossible. To ask for "fully supported" though, when an OS is being sold for say $10 or less... most people these days won't sit around answering phone calls, emails, etc. for $5/$10
per sale.The old anecdote is "...you can please some of the people, some of the time..." This applies to desktops as well. Each person will want things done in their own unique way, and there's simply nobody out there I've met who can predict what the next generation is going to want. From the sound of your post, it looks like you're wanting all of this for free as well. In the end, people strive to make Linux better... simply to make Linux better. MS strives to push new Windows versions out every 2-3 years... because they draw income from it. (Ditto for Mac.) If you want both worlds, you'll have to follow Red-Hat's direction and have a "free" version which the public using it becomes their beta-testers... and have a professional version which basically is paid for through a "service plan" to pay the employees OFFERING the service to the customers. The BETA comes out first (ie: Fedora) and the population beats the heck out of it, RH fixes different problems (in many cases) and when the bug reports begin to dwindle, they copy the BETA over to the RETAIL plan and start a new beta.
Hope this information sheds a little light to the concept of building operating systems. As Microsoft would have told you... "That will be $199.00 USD, please!"