So last weekend I bought a copy of Dragon 127, which I utterly loved as a kid.
Rereading, nearly nothing maps *directly* to 5e (suggested fighter only maneuvers predict Battle Master abilities!), and *everything* is potential. What if you wanted to houserule more elaborate shield use, or two handed fighing? What powers might the magic bows or the most powerful Holy Avenger have? What if your game had big battles to claim a fiefdom, ambush from smart kobolds, or rival martial arts schools?