At the core of the 15min work day conundrum outlined by AngryDM in Tearing 4E a New One: Short Rests and Encounter Resources is that limited player resources can be recharged, largely, by player fiat. The dungeon master has some say, but the fact remains that players have a large amount of control over the recovery of their resources, and so are encouraged to try to do so as often as possible.
Built into the system are a pair of generally minor negatives for taking an extended rest, losing your accumulated milestones and action points, and forcing endurance tests against diseases and the like. But since your daily powers recharge, along with your healing surges, the downsides are almost always outweighed massively by the benefits. Outside of the rules system, there are in game reasons for not takings rests - lack of a suitable resting location and trying to complete a task in within a time limit being the more obvious ones, but the game can start to feel forced if these reasons are always in play. What I would like are rules that encourage players trying to stretch their characters to go through another encounter, and another after that rather than rules that encourage the opposite.
So, my goal is to make the 15min workday a less optimal strategy. To do that I'll look for ways to encourage stretching for that extra encounter while at the same time reducing the overall benefits of an extended rest.
What about limiting the number of healing surges that you regain after an extended rest to be the same as the number of milestones that you achieved before the rest? And similarly only regaining the same number of daily powers?
What healing surges being a "per level" resource, rather than a "per day" resource?
Just combining these ideas probably leaves the players short on healing, and will have them taking extended rests not to recharge healing surges and daily powers, but to recharge hit points without spending surges, and that somewhat defeats the purpose here.
Looking at the effects on daily powers and daily power usage, I think the biggest net result, is that daily powers will be used more sparingly, as you don't gain them back as easily - if you go nova and blow all your daily powers, it could be days before you are ready to do so again - unless of course you push yourself to the limit, by running though a longer string of encounters.
A final, and somewhat unintended side effect here, is that selecting daily utility powers becomes discouraged, as they will be in competition with daily attack powers when choosing what to recharge, when you could just select an encounter power and not worry about it. However, I'm not sure if this is a significant problem.
Guidelines suggest 8-10 encounters per level, and they suggest 3-5 encounters between extended rests. This gives you 8/5=1.4 extended rests per level on the low end, and 10/3=3.3 extended rests per level on the high end. Since the party rests when characters are low on surges, rather than zeroing out their surges before resting, over the course of a level, most characters probably expend between two and two-and-a-half times their surge value in surges per level.
So if we finish off by doubling the number of healing surges each player has to start each level (rather than each day) with, we should be able to limit the extended rest recharge to equal the number of milestones achieved without forcing characters into frequent healing hibernation.