Hi Chen, that sounds a good idea, but there could be two problems, one is that is would be very difficult to code I expect, but then, the other part would mean that it could open some rather large holes in the essential security of courses. Having said that, I have not done any serious coding for over 10 years, and it has really passed me by.
I cannot get past a single course for a cohort wide forum, such as these forums are, well I have always thought they are anyway. Small class forums, teacher forums inside courses Moodle is OK, but for something larger, a site wide, single forum in a simple discussion format in its own course is great. There are other forum tools, bbPress or Vanilla seem the most popular these days, but if you are using Moodle, then you don't have to worry about SSOs or other potential security breaches..
Glossaries can be site wide, or for use in a single class. I have used them in that way, and the Moodle Glossary of Common Terms is site wide, so a global glossary is OK, but again you got me thinking. Can glossaries be placed in a category context? They should be able to... but I have never tried, so will have to try it now...
Common quizzes are always going to be a pain. They are a pain to set up, a pain to administer, even if there are several people working on them collaboratively. But there is no reason why they cannot be set aside in separate courses, specifically for groups of students in connected courses. Access can be scheduled and restricted, quizzes can be made available or turned off according to that schedule.
These things would be part of that common core course we have discussed above, and I have just had another thought.....mmm let me chase it down... might be a while though.