igirisjin,
You're right. In the current state of SMF 2.0 and the ecosystem of official mods and themes we're barely starting to have around it (please do note: I meant intently "official" mods and themes, not third-party only), we wouldn't have good support for all we're thinking of.
But the issue is not really about "removing" anyway: it's about modularity. At the level of the
code (I actually mean architecture of course), SMF should have its components written in a modular way, loosely coupled with the rest, not embedded one in another in a too messy way. And this *is* the clear goal of future versions of SMF: to separate components such that we are able then, to simply tick a box in the installer, and have a calendar - for example - with the forum, or not have it. As a good example there may be some of the current core features in Admin panel: coming by default, but able to be enabled/disabled anytime, perhaps including at installation stage.
For SMF 3.0, we do aim to disentangle the
*code* of the calendar from the rest of the code, and reimplement it in its own files (no, not parts of the calendar code in the post function, parts anywhere else, but a module containing the calendar implementation on its own). Once that is done, the calendar means a piece of functionality which can then be simply added to a forum or a blog,
without direct code modifications. So, no "mods" involved, only the right design and implementation for the functionality, such that it is loosely coupled with the rest. No issue with the download package either: the download package can very well contain the calendar, or the installer can download it on the fly (such as the next webinstaller should be able to do

), and enable it on the forum at admin's choice.