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Are LGA modules that easy to assemble into a low volume product? Castellations would be hand solderable and as a result don't require anything fancy, but would an LGA module need special oven profiles or handling to use properly?  Could limit viability in small production runs, even though the overall cost is probably the cheapest.
USB C would be most desirable to the hobbyist level user, but it probably counts for less in commercial or industrial development environments.  If the mezzanine connectors themselves aren't too expensive, many people probably go that route and make a breakout/development board with the mating mezzanine connectors and the USB C.  That way you have an easy-to-integrate module with a lower base price and a carrier board for more convenient prototyping.
If you were thinking of aiming primarily at the hobby market, maybe the USB C alone would be preferable, since the combination of a module and a carrier board would likely be a fair bit more expensive.
LGA is probably the cheapest to use in production runs, but it would probably be a pain to develop on.  Maybe if you had an LGA module and a USB C carrier board you could develop on the carrier version and then integrate only the module into the product - maybe a good balance in usability and price, especially if the mezzanines are going to be expensive or really low profile is an advantage.