The best way to do the magical item bit is to give magical items to orcs and goblins and whatnot (loot is a good thing). It isn't literally true that every cannon fodder goblin in PF is carrying a potion (that it conveniently forgot to drink when the fight started), but it isn't that far off either. Lots of disposable magic items (potions and scrolls for everyone) will probably fit better than lots of permanent magic items in 5e (and I suspect that is how they will do Eberron and Planescape when they get around to it).
The scrolls would take care of the higher level casting issue as well (especially if they are "you must be this tall" [caster of X type who can cast Y level spells] to use them). It is still a big deal (especially with one shot scrolls), and it rewards higher level casters for being higher level.
The scroll idea is a really good one. Especially if you want to make it rain treasure. Extra loot and free spells all in one.