Has anyone thought this through?

It's the worst idea I've heard since solar roads.

Think about loading the machine with ingredients and how that might work... for each layer (including icing) you'll need different incredient inputs and mixers and perhaps printing heads or methods.

For example, flour, eggs, butter and sugar into one section with an inbuilt mixer. The second input could contain jam and perhaps fresh cream (which will also require an in-built whipper) in the last. To avoid mixing them in the printing pipes/lines you'll have to apply them with separate printer heads.

There will likely be excessive waste and it'll be a bitch to clean.

The only possible shortcut is to sell pre-processed ingredients and then it's just going to taste like ass.