I for one does not like shortening in my buttercream frostings as well, I do have a recipe for white chocolate buttercream frosting that you might wanna try...
3 large egg whites at room temperature
3/4 cup sugar
1 cup unsalted butter, cut into 16 pieces at room temperature
4 oz white chocolate, melted and slightly cooled
In a large, clean heatproof bowl combine egg whites and sugar. Set the bowl over (but not touching) simmering water in a saucepan and heat the mixture, whisking constantly until the sugar has completely dissolved and the mixture is very warm to touch about 2 mins. Remove bowl from the saucepan, using an electric mixer on high speed, beat the egg white mixture until it is fluffy, cooled to room temperature and hold stiff peaks ( mixture should not look dry) about 6 mins.
With the mixer on medium-low speed, add the salt and the butter a few pieces at a time, beating well after each addition, if the frosting appears to separate or is very liquidy after all the butter is added, just continue to beat on high speed until it is smooth and creamy, 3-5 mins more. Add the melted and slightly cooled white chocolate and beat until combined, scraping down the sides of the bowl as needed..... Use right away... Hope this recipe helps and please let me know how it turns out thanks.