Is there any issue with having a Gold Kiddush cup?
Halachically-No, and on the contrary, it is the most beautiful for the Mitzvah. Kabbalistically and traditionally-Yes, as gold is Gevuros, and a cup is the Gematria of Elokim which is Gevuros, and hence it is best for the cup to be silver which is Chesed to sweeten the Gevuros. Practically-whatever you choose is ok.
Sources: Lehoros Nasan 4:25; Igros Kodesh 24:225 that Nishe Chabad gave the Rebbe a gold Becher as a present; See regarding Halachic advantage: Tamid 3:4; Rambam Temidin 1:9; Likkutei Sichos Teruma Vol. 6; Hisvadyus 5747 Vayeitzei footnote 93; See regarding Kabalistic negation: Kaf Hachaim 472:11; Siddur Arizal of Rav Shabsi Mirashkav; Siddur Yaavetz Dinei Erev Pesach 227; Piskeiy Teshuvos 271:23