How tricky would this be to machine? I guess a Triac is not up to the job!

[spluppit]

Personally i would look at away to mill it if possible. Reason is: its hard to define how that clamp was manufactured in the first place. There is a chance it could drop forged and if it is, it will be full of strength in every direction and 'can' be as tough as it gets to machine especially in 316. If its cast it may be better. Like all things like this, you will only know how good or bad it is when you start to machine.

I would steer away from boring due to intermittent cuts, if possible but not essential. Milling cutters are nice and strong and the intermittent cut wont effect a milling cutter. Images can be a bit deceptive but it looks like the rad on the profile does not match the rad center on the inch hole (on the top at least) and it may be very hard to get right in a 4 jaw if even possible. Then you have to repeat 14 times. You could fix it to a separate fixture plate held in a 3 or 4 jaw then calculate the center and put some strategically places dowels to locate it central and use some small clamps, this way you eliminate varying set ups each time, or a variation on this theme would work. A few options to chose from on that theme. In the same breath a plate method could be used to also mill it. The other option if a part dxf is available is to machine the outer profile into soft milling jaws then machine, This would be made a lot easier if the part dxf or similar was available and also cad/cam would help a lot and speed up the process going the soft jaw route. This is how i would approach it as someone in the trade so i don't end up with one launched in my face..... which would undoubtedly hurt a fair bit.

This is an example of a fixture type set up to make life easy.