Custom Gametype Idea

So maybe a concept that's been mentioned before but after playing TFT I started to get an odd nostalgic feeling from my Warcraft III and Frozen throne days. How cool would it be if League came out with its own custom builder and let people make their own gametypes. Small upload similar to what Warcraft used to use. Tower defenses, Zombie games etc etc. I think it would be amazing and who knows another game idea could spring from League. After all Warcraft custom builder paved the way for the Moba gametype that would later evolve from the DOTA concept into League. Any thoughts or ideas?