L'Humaniste is not heavy on gin-tonic, imo. It's very well blended.
Yes. There's longitivity issue but you could fix it by spraying it on your clothes. You can get atleast 5hours on skin, 8+ hours on clothes.
An alternative to L'Humaniste is Atelier Cologne Cedrat Enivrant. Very close at dry-down but the opening is very different.
Almost Transparent Blue is a very clean and modern scent. Safe for office use. Very nice longetivity and sillage. If you like Yuzu/Hinoki this is a must-try. The "screeching lime" (someone said that, I can't remember who) opening might not be your liking, but it will go away in just half an hour. One of the best safe scent in niche IMO.