Ok, so "Remove Vancian Casting" is another option. If we're to do that, what module could we put in its place?
Quite a lot of possibilities. If we're solely concerned with eliminating the 15MWD symptom, eliminating Vancian as part of eliminating hard-coded daily resources would be a way to accomplish that. Casters could work like the Warmage, for instance, having fewer and less wildly powerful spells that they can cast with no particular limit. Or, the game could be encounter-based, with resources refreshing after each each encounter regardless of the campaign's pacing. Or...
Alternatively, what ABOUT vancian casting is problematic...perhaps we can modify that aspect of it (as I"ve mentioned earlier by varying the availablility of spells or the rate of recharge) in some way to discourage the 15mad or encourage the full adventuring day.
The core problem, IMHO, is the arbitrary choice of the 'day' as a recharge cycle. That makes deciding to stop and re-arm a long process that can seem out of place in many campaigns and stories, and a lot less than 'heroic.' OTOH, a 'day' can seem like too short a time to recover from really severe injuries - that's a flip side of the issue.
One obvious solution given the customizeable 'modular' approach that has been promised for 5e, would be borrow an idea from Hero's "Fuzion" and use a "Dial," a rule that changes along some continuum with a setting chosen by the GM. The GM could thus set recovery of resources to generally happen each day, or each hour, or each encounter, or each week, or each 'story' or 'chapter' (thus making re-charging virtually arbitrary). With the ability to adjust resources recovery to his campaign instead of having to adjust his campaign to deal with resource recovery, a big chunk of the issue disappears - the DM is free to keep the number of rounds between recoveries close to the balance-point for the system, consistently and without having to mess with the pacing of his campaign. On the downside, it could turn resource recovery into another 'mother may I' case of DM-fiat.
There's also a closely related issue of class balance, if some classes have daily resources, some encounter resources, some unlimited-use resources, and others varying combinations thereof, then, if daily resources are compensated for their reduced availability with greater /power/ than encounter resources, which, in turn are more powerful than unlimited-use resources, then class balance is completely thrown off anytime the number of encounters in a day or rounds in an encounter deviate from whatever norm they were theoretically balanced around.
One very powerful and effective solution to that problem is to give everyone the same proportion of such powers. The powers can be quite different, they just need to be comparable in power and number at each level of rechargeability. The 15MWD remains, but it no longer trashes class balance.
Another, would be to do what Hero System and some other games do: make limited use powers 'cheaper,' but no more powerful than other powers. Thus, for instance, a wizard might know dozens of spells and be able to cast 10 of them each day, and they'd each do very different things, giving the wizard a great deal of versatility and the price of a good deal of resource-management headaches. But, they wouldn't be a source of severe class imbalance if they were no more powerful than the basic abilities of classes with unlimited-use abilities (who would simply have only a few such, by way of compensation). That could, perhaps, be an even more radical departure from D&D tradition than was AEDU, and it probably wouldn't be as robust a balancing mechanism - tending to make the more versatile classes have more stunning spotlight moments when they have just the right spell for the job, but also leaving them sadly non-contributing when out of spells.
IMHO, the best solution might be to combine the "Dial" option with classes getting the same proportion of unlimited-use and limited-use (how limited based on the dial) abilities. In that way, there's no need to coerce resource balance to retain class balance, and the DM is free to run the campaign at a pace he and his group find reasonable.
As it stands, WotC is doing the same "add advice, but not mechanics" to work on the 15mad. That may be fine for some and not for others.
It's definitely not fine - personal preferences aside, if for no other reason than that it abandons 5e's mandate to be 'inclusive' by spelling out a 'one right way to play.'