Here's my idea:
*Unless two milestones have been reached, following things happen at extended rest:
-Regain 1d6+CON modifier HP
-Regain 1d4 Healing surges
-Roll d20 for each unspent daily power starting with lowest unspent daily power and continue towards highest. Roll items before actual powers. Regain first daily power on roll of 19-20 and continue. You may regain another on roll of 20 and then stop. Roll only once per power. You can potentially regain up to 2 powers, but are more likely to regain none.
After reading this, I find it a bit confusing, if You find difficulties understanding this, ask for explanations and examples.
P.S.
And of course, this is intended to stop players from abusing 5 min work day, and leaving dungeon after every two rooms so they could rest somewhere safe. If dungeon is cleared, or is at an obvious pause, let them rest normally even without 2 milestones.