Caperitif is an aromatised wine made by infusing Chenin Blanc and Muscat wines with Quinchona bark (quinine) and 34 other botanicals, many of which are...
Caperitif is much less bitter that Campari, but it might substitute the vermouth. Caperitif is likely more bitter than the standard red vermouth in a Negroni. Maybe stay in the bitter and white-yellow style and also substitute Campari with Suze. Best luck.
It’s more in line with Cocchi Americano across and Byrrh and maybe the European version of Dubonnet. The US version I have just taste like port and I’ve never had the European version of Dubonnet.