Lovely cocktail, one of those favourites I don’t have so often, because, as you say, it might need adjustments depending on the ingredients at hand. My favourite way to do this is 100% “à la française” with Giffard’s Abricot de Roussilon, a very smooth but little oaked Ch. de Breuil calva, and Citadelle dry gin. I sometimes add a splash of Pernod absinthe if I am in the mood for something slightly more on the dry side.
Thanks, I much appreciate expanding on low alcohol drinks like this one. Schweppes tonic did a good job — the crispness suits it well. One basil top was also an excellent complement. I also agree that it is absolutely possible to play with proportions here — Byrrh and tonic is an excellent combo on its own!