Haut-Medoc

This is really intriguing. I've never seen the Maurin Quina before and will definitely look for it. I'm wondering what would happen if Cherry Heering or Combier Rouge were substituted for the cassis here.

I tend to think about cocktail development in terms of flavor or aroma accords. In this cocktail, I was thinking about the bitters first - they're fruity, with a chile spicyness and typical bitter notes. That led me to Cassis, which is fruity + a woody bitterness, which led me to Rye, which has a green, woody bitterness as well. Maurin Quina is cherry + almond + some interesting bitter notes, and the rinse of Creme de Cacao is meant to mimic the 20th Century cocktail, as well as to tie in and harmonize the other flavors, all of which go well with chocolate. This is still in the theoretical phase, as Maurin Quina is a special order only thing where I live ;) 

But to answer your question... I think that other cherry liqueurs might be a good substitition, as long as they have a bitterness to them. You might also want more lemon juice in the cocktail to make up for the loss of acidity in the cherry liqueurs.

So I'm busy today. My likker store actually sourced a bottle of Maurin Quina for me, and I made the drink as written (the bitters are dropper instead of dash). I like this, if I do say so myself. It tastes like a good left bank Bordeaux in a weird way, with woody notes forward, cassis and red fruit in the midpalate, then the bitterness of the Maurin Quina mixed with the chile-accented bitters on the finish. I think a bit of extra shaking is a good thing as it brings out the brambly Cassis more.