The answer is simple, if you do it for one person, then you'll have to do it for everyone else. That means every other hat that is similar to a gst hat will have to be changed/removed.
If the rules would have been more strict from the beginning, then we would not be having this issue. The whole sparring community has been pretty greedy for years, myself included. We want really nice hats, and sometimes the hats are nice, but we still want them to fit our needs.
Holy tried to make a gst hat's visor be transparent, and it was accepted. Some people complained, because they had requested edits for their hats before, and their requests weren't approved, so rufus reset holy's hat to what it originally was (to make it fair for everyone)
Since the whole community is selfish whenever they don't get what they want, and some might, then that leads to everyone being treated equally, and no one gets any special treatment anymore.
In this case, if they do what David wants, then they also have to remove every other hat that is an edit of a gst hat.
If they do an edit for a team, then every team will want an edit. (The problem is that not every staff wants to edit their hat, and sometimes the people who request an edit basically want it remade)
Unless they start doing the other two, then it's only fair (for now) to keep selling remakes.
I believe that, in their minds, they are thinking "why waste a very nice hat on just 7 people, when I can make a nicer one to sell at nexus." That's why the cat hat, the nub hat, and many other gst hats have been remade.
If we continue to be greedy, then the gst reward quality will be reduced due to all the limitations.
Also, leah doesn't really have a say in what gets approved and what doesn't. She probably didn't even know that a cone hat existed already. Might be hard to believe, but she doesn't really hang out in BA.
The sparring community and the gfx staff members have been clashing for years. I wouldn't be surprised if they stopped caring altogether, since it's not like anything could done about it.
In the end, I could care less if David gets what he wants, or if any of my gst hats get remade and sold, but it wouldn't be fair for everyone else. It will make staff look bad, if they comply, especially after an item has been given to a lot of people.
TL;DR
The only time that staff change a hat is when there is copyright infringement involved.