I try to deal with this by tying and carrying both a "plain" and "fancy" version of each nymph. I tie about two of the plain version to each of one of the "fancy" version. The plain nymphs are fast, easy suggestive patterns and the fancy versions are more immitative. Some examples of plain versus fancy:
BH greenweenie/ Green Rock Worm
BH hare and copper/ Crane Fly Larva
EZ Stone nymph/ Goonie Stone
BH Pheasant or Turkey Tail/Baetis and Paralep nymph
Flashback Iso/articulated iso
BH Flashback Hare's Ear/Steno nymph
BH Flashback Sulfur/Dark and Light Ephemerella
sparkle caddis softhackle/pharate caddis.
For boxes I just wear a chest box now for about 90%of my fishing. My three year round trays are:
Anchor nymphs and streamers
micro patterns-midges, tricos, blue quills and olives, and small nymphs (PT's, caddis larva, shrimp and cressbugs.)
Soft Hackles and Spiders. This tray also contains a handfull of terrestrials.
Later in the year I add a caddis tray and then a sulfur/cranefly, yellow sally tray.
In my vest, when I wear it, are boxes for large dries, big streamers and wets, terrestrials, and a general duty box for catskill dries, extra streamers, the immitative nymphs, egg patterns, and winged wets.
BTW, one of the best Fly fishers I know uses the BH hare and copper 10-18 in a variety of colors for most all of his nymphing. So I think simplistic is fine.