Because pickling ingredients vary, different cornichons will produce interestingly different results and complement different gins. I've been happiest with Hendrick's so far. A bit less complex but also good are traditional London dries.

The hot sauce is a necessary finishing touch that only occurred to me after tasting the first iteration. Use something flavorful with a hint of sweetness, rather than just a Scoville bomb.

To get watermelon juice: For just one or two drinks, scoop or spoon out chunks of watermelon into a citrus press, such as a handheld lever type, and press firmly over your jigger or a glass. You should get about as much juice per squeeze as you would from half a lime. For a larger batch of juice, blend the watermelon, and strain through a fine sieve.

Père labat Soleil, is a gold agricole rum, aged 6 months in barrel, still very young but very different from a white one. Very nice.
Cuban rum is added to up the proof without giving too much flavor and balance the whole thing.

Floral and light.