Allow use of flavour transformers in UserSettings

I like how I can add toppings (= flavour transformers) to my flavours on the command line. However, I cannot easily do so when writing a custom UserSettings, due to module dependencies. Instead, I have to copy and paste code to get the same effect -- or manually apply the topping from the command line, on top of my custom flavour (which partly defeats the purpose of the custom flavour).

EDIT: Actually, it's even worse: I would like to base my userFlavour off developmentSettings, but I can't do that. :(

Can definitions be shuffled around to make this easier?

Thanks!