Teemo should passively get XP and Gold while in stealth for long periods of time
Think about it. This wouldn't affect laning, where he could stealth, last-hit, stealth, repeat, to get level 18 first. I mean Teemo should be rewarded for stalking someone's jungle for long periods of time to be the obnoxious little shit-stain he is.
If a Teemo wasn't punished for doing that, just imagine all the atrocities he could commit! Patience is key to a good trap!