well i decided to build ad/ap kassadin in a custom bot game because i dont want to risk losing a game for my team with a dumb build but here it is. worked pretty welln and was quite fun. farming was very easy and nobody can escape you. this build may be a little unrealistic because of easy kill bots but i was lagging at the time so it was still quite difficult. so sapphire for the mana, sheen for the bonus attack after a teleport + ap. phage for some hp,att, and a slow. nashor's for att speed, ap, cd reduction, and mana regen. rageblade for more att damage and ap and some atacking ap and attack speed. lich bane for the ap damage that now exceeds att. frozen mallet for some more hp and a 0 chance of escape. and finally a hextech for life steal and spell vamp, perfect for your ap/ad build, more att and ap and a nice bonus burst and better slow. survivability may be a problem with this build but i never had too much of a problem against bots of course.

[RIFTWALK] -> [NULL SPHERE] -> [FORCE PULSE] -> SHEEN/LICH/NETHER BLADE Activate -> Auto attack, rinse and repeat.
this should do a hefty amount of damage with 500 alone from lich bane+ 80 extra for 5 seconds, 500ish from null sphere, another 500 from force pulse, 220 from rift walk, 300 from hextech. this FIRST burst is 2100 damage not including auto attack and 410 healed. this should be quite sufficient for taking down there ranged carry or any other squishy character.