This question is almost impossible to answer without including a lot of "but"s or return questions.
First of all, when you talk about multiple calendars per site, are you just talking about the UI but also about the data management in the Repository-tier? Because then you are opening up another can of worms relating to the components handling calendaring data, which are quite monolithic and wired to only deal with one calendar.
Second of all, when we talk about "can this be done with Aikau" the default answer will always be "yes" since you can usually do anything with software if effort / cost is no objection. How much effort would it be? I can't say - I am not aware of anyone having built a calendaring UI with Aikau, but this is mostly due to the fact that Aikau has not been around that long and hasn't been adopted by too many people yet (or they have kept quite about it). Out-of-the-box I am not aware of any modules that would remotely support calendaring use cases. Aikau has the goal of making it easy to create extensions and custom modules that may add such functionality, and from my experience so far it typically is easy to add new features if you have a solid background in general web development.
