Quick reply...
How many people know that hildon-banner is capable of displaying not merely plain text, but text with Pango markup?
The proposed feature is to enable espeak announcement (espeak saying aloud the text at the same time it is displayed) within hildon-banner. It should be turned off by default, and the turn-on switch should be a key within gconf. Then, the graphical user interface for espeak hildon-banner announcements could be part of profile (General, Silent) settings (along with system sounds, email, SMS, vibration, and so on).
Just a thought. Since hildon banner is not a standalone application or library, but part of hildon, it would be nearly impossible for me to compile, install and test a modified version of hildon. I am not nearly enought acquainted with git and makefiles for this. And hildon is too important part of operating system to tweak it without any prior experience.