HI Michel. Nice design. You are right that the repousee is the way to go. Federico is right in that chasing is part of that process. What you will need is thinner gauge silver sheet, the right chasing and repousee punches (and tools) and a little experience or experimentation. I would be easy to punch through the metal
. You can try it yourself but practice first with copper sheet for a while until you get the techniques down (along with books on the subject), or.......you can send it to me.
(shameless, I know). Looks like the next thing to work on is the bottom chape. There are other considerations too, like the patination of the silver, the soldering of the silver, the fitting of the cloth, etc, etc...a long process.
One other note, you may want to consult the book "The Treasury of the World" that has lots of expensive Mughal khanjar chape designs from the museum in Kuwait. Wonderful resource.