Guys/girls/Players I want to play Katarina but not as AP but as AD/other.

You can play any champ however you want however when Riot releases a champion, they usually have a playstyle in mind and balance around that. She is meant to be an AP assassin and her ratios and skillset reflect that. She is an awful tank as she has no real innate tankiness besides the very brief shunpo reduced damage. She also has no CC so again, tank out the window. You could build AD, capitalizing on her ult and her W, however she is designed to burst down people over and over because of her ratios and passive. As AD, you could jump on someone and attack them, but not burst them the same way so you'll just get CC'd instantly and most likely die.

There are alternative builds for many champs. Ekko can be tank or AP Assassin, Udyr can be tank or devourer onhit, Ezreal can be AP or AD, Kog as well. However with Katarina, she's fully balanced around AP. The AD ratios are there so she can synergize with gunblade, not so she can see AD builds.

AD assassins benefit from stacking armor pen whereas all of Kat's Damage is Magic, so her kill potential will be very low = no resets.

Bruiser/Tank Kat is also very weak because unlike Diana/Fizz/Akali/Ekko she does not deal any extra damage through auto attacking (also means no resets).

Don't mean to be a downer, but its been tried and falls flat.

I remember seeing the rare jungle Kat in season 3 or 4, but her clear was always very slow and dangerous and she was extremely vulnerable to invades. Don't think Runic echoes changed that either.

Note: Just because a champ is a one trick pony, doesn't mean she isn't fun ; )