No matter what you do when you work with enamel (especially
transparent and translucent), it is always a good idea to completely
deplete your silver or your gold (unless you are working with 24K or
fine silver). Any contamination from other metals except platinum
will react with the pigments in your enamel. In order to obtain
optimal results, I always do this.
I am not sure about your heavy plating idea as I have never done it
but it does not sound like a good idea to me as I am afraid that the
plating might disappear with the multiple firings.
Why not use the traditional 24K gold leaf method sandwiched between
layers of enamel?
You would first fire a very thin layer of transparent high melting
point enamel onto which you will apply your sheet of gold with a
paint brush and some clearfire so it sticks. Fire again and prick
any large blister with a thin needle and gently press the blisters so
your gold surface is as smooth as possible. You want to minimize air
bubbles trapped in between your first enamel layer and the gold leaf
or paillon. Then enamel on top of it with the colors of your choice.
The reason why you still want to deplete your metal is that you don
want the edges to have a different color imparted by the alloys
reacting with your pigments.
If you want to have the silver plated after the enameling process
when your piece is finished, it is a possibility depending on the
kind of enamel you are using. I would always have a sample to try as
some enamels could get duller in the plating procedure. In most cases
there is no alteration of the enamel.
I hope that it helps.