I add your suggestion to the list, thanks for that. I can't promise they will come (soon), though.
However, some issues remain:
Oldest (same with N/E/S/W) requires a manual list for every country. It has to be maintained with seconds/thirds, because caches may be archived, although that would be only a minor problem. Bigger problem (for N/E/S/W) is: Say you found the northernmost at that time. If a cache gets published that is even further north, you would lose the award. We want to keep awards permanent, whenever possible (sometimes it might not, see Jasmer, Favorite or Author badge, or Country badges when there is some political change).
A non-PGC option for European countries might be geotrophy.net, where you can manually generate badges for NESW,oldest,highest,lowest for European countries.
Distinct cache types has been requested a couple of times, it is on the list, we have to get creative there though in terms of implementation. The AddOn should be a "goal to achieve", not necessarily a "current status". So it would be rather an AddOn for say "Diamond Diverse" in a country than an updating number.
Limited space: We are limited to 6 AddOn slots, and are currently using 4 for Countries. So we won't be able to implement everything. :)