You have realy pulled one out of the hat for responses with this
one. Can I suggest that you use a combination of two processes
that is etching and krause bur. Etch your design to about 75% of
the depth of your metal and then take the remainder out with the
bur. With the metal being thin at this point you should have to
use only very little pressure to remove it and also have a
sholder to cut up to.
Well you have plenty of options to try. Let us all know how it
turned out when you have finished.