Beorunna's Well also has the benefit of being an iconic location in the Realms, while the other burial mounds are not. So that's cool.
In regard to using good dragons...I hadn't thought of that, but it's an interesting idea. You could probably tie it back to Felagos (spelling?), the good dragon flitting around SKT, or even Klauth. In my campaign, Imryth is the big bad guy, and she leads a whole clan of dragons that the PCs must overcome. At low levels, the PCs will fight her children. At mid-levels, the PCs will fight her consorts--these are the dragons that replace the burial mound fetch quests. And at high levels, the players will fight Imryth herself. At least, that's the plan. The PCs are 4th level and are probably a few more sessions away from having to face their very first dragon.