I'm with TV that cassis=lime, otherwise it's overpowered.
I had 45\20\20 with mezcal topped with FeverTree Light Ginger ale.
The excellent ginger ale helps make it. mezcal
The mezcal stands out despite the oomph of the lime and the FeverTree. Amazing.
Just tried it. Well I am not especially fan of cassis, but I loved this cocktail. I also saw this recipe in a tiki cocktail box, I think they recommend it with tequila blanco. I might try another time