SodaPOP326 this has been suggested many times its not going to happen any time soon.
http://bugs.winehq.org/show_bug.cgi?id=11112 Yes this bug is a big start of problems. Wine itself is not multi user.
Next wine itself is still having work done so it can get performances better than half that of windows for a large number of games.
Lets go down your points.
1. It would possibly run great on a system that cannot support more than bare-boned Windows XP.
True but a machine like that may bring its own problems. Please be aware that wine brings some of its own overhead. So not all applications running in wine use less resources. Some require more. Wine sometimes uses less but also uses more.
2. Running Windows programs on a ext4 partition would be very reliable and fast.
Not exactly true either. btrfs with its snapshotting is a match up to NTFS. Apples against Apples. btrfs
not exactly the fastest. ext4 has many advantages over fat32 but is not exactly a head of NTFS for reliability.
Equal grade file-systems the performance is close to the same once you add in wine own overhead.
Problem here is when it comes to games most games are not disc IO bound they were designed for the fact Windows is slow doing this. Most games are CPU and GPU bound. The GPU bound is a major problem.
3. Individuals Running WineOS would save about $200. (That is my estimate of how much Windows costs

)
Even 200 dollars over a live of a machine is not too bad. But the real price is 150-20 USD(yes depending on volume acquirement).
4. Imagine gaming with WineOS! Windows games would run a lot reliable then Windows due to the ext4 partition.
Lot of game reliable issues happen under wine as well. Due to bug for bug compatibility. Running wine does not help here. When wine started the project goal was a bugless version of the Windows ABI/API problem is bugless version will not run many programs.
5. Wine could have a install wizard that allows the individual to pop in a Windows disc and install native DirectX or Windows system files.
Not wine objective. Wine will never be extracting files from Microsoft Windows install media. Wine objective is to be able to run without native Directx part or system part from windows where possible. Currently all the parts wine normally replaces are gettable from run-times Microsoft provides. Using native parts removes wine options to use short cuts to native for higher speed.
6. You could still use Linux programs to your own liking
Yes this means wine would have to package up a Linux program Windows manager as well.
Maintaining a full Linux distribution takes lot of resources. Those resources at this stage would be better targeted at fixing wine major bugs like poor performance due to not exploiting video cards effectively.