A few suggestions:
Branching Evolutions (pick 3): Gloom, Slowpoke, Poliwhirl, Snorunt, Kirlia (all have branching evolutions).
Pseudo Pseudo-Legends: Larion, Vibrava, Fraxure (All high-stat, late evolving, 3 stage lines, but not pseudo legendaries)
Shadow Triad: Sneasel, Murkrow, Houndour...