If your friend is Catholic, the cross can definitly have stones on
it. As a matter of fact I remember seeing antique pieces from France,
Italy and Spain very heavily jeweled, especially when belonging to
the old aristocracy (most commonly used were garnets, amethysts,
onyx, jet, coral (especially Italy) and sometimes even diamonds or
the great three (rubies, sapphires or emerald particularly in Spain).
Not all of them even had a Jesus on the cross.
When I was still in Europe I help a client sell a nineteen century
family rosary whith a cross set with old mine cut diamonds. The back
of the cross had an enameled and jeweled Jesus. The cross was hinged
and allegedly contained a piece of the true cross.
Anyway for the cross I can assure you that stones are acceptable.
Most of the rosary I have seen had a picture of the Virgin Mary on
the center medaillon if I remember well. The one with the diamond
cross had an entaglio with a profile of the Virgin Mary surrounded
by diamonds. The beads were in faceted rock crystal.
I can’t say for sure if a dove for the center medaillon would be
acceptable but I can’t think of any rule against it. The most
important is the symbol of the cross and the 59 bead sequence so it
is “functional” so to speak.
I have seen antique Catholic crosses with the top part made of a
stylized dove. The head formed the top part of the cross, the wings
the arms and a gem dangled from the feet to form the bottom part of
the cross. These were popular I beleive from the seventeen century
until the nineteen century= in regional French jewelry (maybe other
Catholic countries as well). Most of the time they were made of
silver or vermeil set with paste glass. Those with diamonds were
rare. Of course they were just crosses and not rosaries so I can’t be
positive about the use of the dove in the rosary center medaillon.
The dove was certainly used by Catholics as a messenger of peace so
your idea sounds very appealing and not strange at all.
I would ask your friend what she thinks about the idea. She is the
one who is going to use the rosary and maybe the ideas of the dove
and peace mean a lot to her.
Best of luck with your project.