I too get complaints from some of my community members about the removal of the View Source (since it exposes the HTML vs BBCode) - I was surprised to find that many people mark up their posts prior to posting.
I get that, but with this version of the CKEditor, using keyboard shortcuts is a HUGE time saver, and much easier to mark up than manually writing BBCode, much less HTML.
Since I upgraded my forum to 4.x I have been loving the ease at which I can CTRL+B to bold, CTRL+I for italics, etc. - not to mention the paste and upload image capabilities.
Your forum may be geared towards more complex markup and hence why BBCode is important to you/your community, which I can understand.
IPS seems to be taking the "greater good" approach in abandoning BBCode (presumably to make the software easier to maintain and improve upon), but if it's feasible there should at least be BBCode support for those who want it (or if possible encapsulate it into an addon/application) as you suggested.