I think there needs to be some sort of mechanic to handle low level, NPC spell casting. It's nice if a village temple has a servant of the gods who can actually cast minor divine magic. Also, it would be great if villages had a local sage/herbalist who was knowledgeable in the arcane arts.
If the PCs are supposed to be special, but the world more fantastic, then there needs to be a bridge between the two. NPC spellcasting classes filled that roll in 3e, so I think something is needed for 4e.
On that note, I would love to see a list of "utility" spells included in the DMG. These would be common spells that would impact every day life, but wouldn't be useful in an adventuring situation. Maybe these could be low-level rituals.
Some Divine examples:
Bless the Crops - gives disease resistance and an extra 10% yield to the harvest.
Cure Illness - like Cure Disease, but for the sniffles as opposed to Mummy Rot
Purify Water - already a spell in old editions, but seems useful for a village.
Read the Stars - astrological bonus to some community effort
Bestow Child - a wedding ritual that gives bonus to baby-making
Some Arcane examples (similar to 0 level spells):
Pyrotechnics - make fires spark and flare with colors
Light the Wick - Instantly lights candles, torches, hearths
Ghost Hand - small objects float to your hand when commanded (use the force!)
Mend Object - repair broken mundane objects
Minor spell like these, available to NPCs, would help the D&D world seem more fantastic without filling it with 1st level adventurers or retired heros. 3e's Adepts and Magewrights fit this bill.... but I always felt something was a little off with them. What's the point of a 20th level Adept? Wouldn't a 20th level Magewright eventually just become a wizard?
I'd like a single stat block each NPC class; maybe an apprentice and a master, which could be customized by a DM if wanted. Just list average stats, a single set of combat stats, standard skills w/ points already added, and a list of spells/powers.
If Thurgood, the Master Blacksmith, is the best smith in 100 miles, then as a DM I'll just give him a +5 to his Craft skill. No need for me to add levels, calculate BaB, HP, individual skill points, etc, etc.