Actually, that's not quite accurate as it does not account for the number of Squads you have in each. Your assumption that "A" is the answer might be different if you already have 800x of Blossom Mages but only 100x of Rangers. In that case, producing Rangers makes more sense.
This actually doesn't really matter; your existing squad count doesn't impact the marginal value of each subsequent unit produced in this case. The only way it would is if your unit production exceeds your total possible unit usage (i.e., you can clear Spire and 6* every single Tourney province available with less units than you create each week). Frankly, that's just not the case for anyone.
If we started adding in a conversation about how many frogs you should be building vs blossoms, then it would matter -- you'd want to make sure you have enough frogs and blossoms to handle their respective jobs -- but in this case, just talking about Buds/Blossoms and Archers/Rangers, it doesn't. You can build blossoms and archers and handle all necessary Mage and Light Ranged jobs, without ever building Buds and Rangers, and you'll be better off doing that (regardless how many existing squads you have) than you will be by building a mixture of all 4.
What I'm really hearing from your comment is that you see an inherent value in 'balance' -- that you believe having equal numbers (or even just a healthy mix) of various troops is a good thing in general. Because this game is inherently unbalanced, having a balanced army is actually a bad thing. You certainly do need to have some level of balance across unit classes (i.e., light melee/light range/heavy range, etc), but having a balance between individual units is not necessary. I understand placing value on balance -- the game tries to tell you that balance is important, and that building and training some of everything is important. Unfortunately it's just not true. In fact, it's detrimental to your progress to build/train some of everything. This is not a balanced game, so our approach to it should not be balanced either.
NOTE: I want to make a caveat there. If you enjoy manual fighting, and you enjoy fighting with all different units, then by all means train them all. The *real* goal of this game (regardless how much I and anyone else talk about 'maximizing value' or 'optimizing performance') is to have fun. For a lot of us, maximizing value and optimizing performance *is* the fun part, which is why we focus so heavily on it. If that's not you, then ignore this and do what you want.