Something similar was suggested a while back, but I'd like to expand on it.

The ending of the Hoar temple quest is neat, since you can keep going. But what about if the person GIVING the quest allowed you to take extra goals for additional pay? It could be to kill an extra dozen bad guys, or fix a broken pipe (Craft Trap check), or to rescue someone on the inside while they're fighting for their life (have the NPC spawn as the PCs enter the final room, and if he lives they get the bonus).

And how about exploration XP for all (or at least more than just one as it is now) QA's I'd hope that would give players an incentive to do more quests at least once that are rarely taken, there's such an over-abundance of quests and I pretty much get to do the same old ones over and over.

Exploration XP for quest areas is a great idea, along with putting additional conditions on the quest. In Fable, which was a so-so game, they allowed you to tack on conditions to each quest in exchange for an extra reward. Concealing extra tasks in the conversation with certain NPCs would be a good way to keep people from clicking through the dialogue and ignoring it.

For example, you may be required on the Brewery quest to collect every bottle of watered-down ale in the building and bring it back to Mord. On the Rat Barricade, you may be paid extra if you bring the flame gusher back fully charged. For the Clowns quest, perhaps there is a teddy bear somewhere in Clown Land that you have to Search for (a placeable trap door that leads to a couple extra clowns and the item, hidden randomly in the quest area). Such.