Eh. I don't see the issue with dangerous terrain or vertical teleports, honestly.
If I put dangerous terrain (clifffaces, pits, lava, whatever) into my encounter, it's because it's supposed to be there. If anything, I cheer the idea of teleporting/shoving people into it.
Teleporting vertically could be nasty with the right build, I guess, but most of the time you're giving up an element of control (teleport) to have a 45% chance to do extra damage and knock them prone. Unless I'm missing some powers which generate Harrowstorm-like distances, I don't think it's that big a deal (and before someone points out saving throw penalties: that's a whole issue onto itself).
EDIT: A quick compendium search gives me these results for "teleport the target" that are not restricted (and thus allow vertical teleports):
Dimensional Vortex, Swordmage, Level 3 Encounter. 5 squares.
Be Gone, Swordmage, Level 9 Daily. 5 squares.
Wormhole Plunge, Ardent, Level 1 Daily. Wisdom mod squares.
HammerFall Step, Arcane Wayfarer, Level 11 Encounter. 3 squares.
Forcing the Portal, Blade of Cendriane, Level 11 Encounter. 2 squares.
Will of the Feywild, Feytouched, Level 11 Encounter. 5 squares.
Argent Arrow, High Forest Scout, Level 11 Encounter. 1 square.
Probability Travel, Storvakal, Level 11 Encounter, 1+wis mod.
Sequestering Word, Avenger, Level 13 Encounter, 5 squares.
Astral Fury, Avenger, Level 17 Encounter, 3 squares.
Sprite Dance, Seeker, Level 17 Encounter, 5 squares.
Planar Shock, Swordmage, Level 19 Encounter, 10 squares.
Celestial Seal, Celestial Scholar, Level 20 Daily. 3 squares.
Excoriating Challenge, Avenger, Level 23 Encounter, 5 squares.
Fetters of Darkness, Invoker, Level 23 Encounter, 5/10 squares.
Wildrift Burst, Sorcerer, Level 23 Encounter, Dex Mod + 1d4 squares.
Shuffling Thunder, Sorcerer, Level 23 Encounter, up to 10 squares (d10 if Wild mage)
Western Wind of Storms, Shaman, Level 25 Daily, 10 squares.
Shifting Wave, Spellscarred, Level 27 encounter, 4 squares.
Enthropic Whirlwind, Sorcerer, Level 29 Daily, Dex mod squares, and up to 5 squares UEOE.
Prismatic Wall, Wizard, Level 29 Daily, 5 squares.
While a few of those are problematic, it seems tough to really make a 'teleport' build to abuse this.