Perfect proportions, contrast, power, complexity, refinement, heritage, presence, and absolute size. I'm not a fan of tribute watches, but contemporary JLC should look to the key traits that define this watch and seek to implement them in new references. The balance of tones, character, and upscale aura were achieved without resort to cliches like size or PVD, and the style owes almost nothing to retro design philosophy. Even better, it doesn't really look like anything any other manufacture was producing at the time, so this Master Geo is a true original in that respect as well.
Regarding the hunter caseback, it's true that these are entertaining, but I'm not sure that it's worthwhile if it would add thickness to this example. On the 18K gold models that employed the hunters, I always saw it as a mark of honesty since wrought gold is far more expensive than sapphire, and it avoided the appearance of price cutting on a precious-metal watch. It was almost like the old Patek, Vacheron, Blancpain, and Roger Dubuis models that would ship with an accessory solid gold caseback to assure the client that full value was being provided. But on a steel watch, especially one with an excellent thickness-to-diameter ratio, the hunter might have disturbed the fine visual and ergonomic balance JLC achieved.
Best,
Tim