Some suggestions

Make the sacrificial jaws from a wood softer or as soft as the
wood you work with. Better to dent the jaws than a part you're
working on.

Put a slight slope of both sacrificial jaws so they angle towards
each other. If you start with the jaws like this |____|, when you
apply clamping pressure they'll want to do this \____/. But if
you start out like this /____\ (exaggerated of course) then when
you apply pressure you'll get this |____|. For jaws this height you
could run the boards through a planer, with maybe two playing cards
thickness shims under one edge. Doesn't take much slant but having
some helps - since this kind of vise seems to always have some
slop in the mechanism.

Notch the bench top so the inside - plus a sacriifical jaw - come
out with the face of the inside jaw flush with the front of the bench
so you can clamp horizontal parts to the bench apron.

I'd skip going with dogholes in the outside jaw and go with some kind
of end vise (the Veritas Twin Screw is great - for all kinds of holding
tasks).

If you build another bench - get ALL the vises and hardware - BEFORE
starting the design. "Adapting" later can be a nightmare in the making.

charlie b