The fastening strap is a good idea and looks like it would work better than a hammer thong.
I'm wondering if you folded up a thin skirt of leather web in the opening, even just for part of the way to protect the interior holster & gun from debris or water entering in.
Would it still draw as well?
A thin web that would still allow the holster to open up a ways, and strategically placed so as to not interfere with the holster opening up to draw the gun out.
If that would defeat the purpose of the opening in any way then disregard this idea.
The ease of draw intention seems like a really good one.
But I would not want anyone to think that the muzzle could pop out through the front opening if the holster loosens up with age or if the strap comes undone, and I'm not sure if dirt, sand or debris could enter and accumulate in the holster, or scratch the gun over time.
The leather does looks thick and very stiff though.
The holster is also a very nice color which I like a lot and it looks great.