I agree about the arch but its hung on original (pintle)side hinges set into sandstone. the latch is also set in sandstone. these allow for about 40mm thickness. I can't help but think any gate will look a bit untidy at the top.
I did a side gate for a customer end of last year. They struggled with a design and it ended up just being a curved top side gate. I made the boards different widths to try and add a bit of interest. I think quality hinges and latch make a difference.