There's a world of difference between coconut oil and Kremelta NZ [copha AU].
Coconut oil is either an unrefined [virgin] or refined vegetable oil that exists in a semi-solid state at room temperature. It melts around melt at 24°C.
Copha and Kremelta, on the other hand, are hydrogenated coconut oils. Hydrogenation changes a liquid vegetable oils to a semi-solid fats [partial hydrogentation like Crisco] or a solid [full hydrogentation]. Copha is block solid at room temperature. It melts around 38°C. I was under the impression that Kremelta was the same consistency. A texture like peanut butter is not what I envisioned.
All vegetable oils have different densities. Coconut is one of the denser oils. Coconut cream will "dilute" the mix but it will not change the inherent characteristic of a hydrogenated oil to harden at room temperature. The frosting should be "lighter" in texture but it will still "crust" or harden at room temperature.
Shortenings are available from foodservice and catering supplies. Try http://www.gffoodservice.co.nz [look under "bakery fats and oils"]