this is what is an ideal teemo build for late game adc assassination

also consider replacing ludens with 
from stealth you can oneshot an adc with Q auto and the gunblade active.
there are few other teemo builds. there is the bruiser ad frozen mallet build. which u build frozen mallet into botrk and then somewhat tanky.
there is the on hit build which is explanatory. attack speed on hit items.
the problem with anything but ap teemo is that. you have to be autoing to do damage. teemo isn't gonna get peeled for. they gonna peel for the adc. hes immobile and gonna die easily to a single burst combo from a mage or an assassin because you have no heal.
the problem of ap teemo is that you get all of the enemy team spamming 2 oracle altercations and making your shrooms useless. its stupid. really reduces what teemo can do.
its not a bad build at all you have there but you don't want to go ap without buying liandries.