"Takashi Tezuka and Yosuke Oshino – the Producer and Director, respectively – recently spoke a bit with Nintendo Dream. Yoshi was eventually brought up in the conversation and it was revealed that the character caused some controversy on the team. Tezuka was adamant that they ensure he appear in the game, but the team had to think through how he would behave in certain situations, such as how he responds to Boos and what he could and couldn't eat. Here's the quote:

     Oshino: We decided to put in characteristic actions like Raccoon Mario, Caped Mario and Propeller Mario during the first phases of development. But Yoshi had much controversy...

     Tezuka: I was a bit pushy in requesting to have Yoshi. There were reasons like being responsible for the Wii U game Yoshi's Woolly World, wanting to use the Yoshi amiibo, and wanting to have some kind of collaboration as it is also Yoshi's 25th anniversary

      Oshino: But adding Yoshi was complicated, so we discussed what should we do. In Super Mario World, you couldn't enter a Ghost House with Yoshi for example. As you can freely arrange things in this title, there were many occasions in which it was required to think about how to apply things that you couldn't do in the original game, like whether or not Yoshi can step on a Boo and what Yoshi can eat and what he can't."

     I'm personally surprised that there was any debate regarding Yoshi being in Mario Maker! Eh, all that matters is that he's in the game. SMM would be a pretty bad game without all those levels where you have to sacrifice Yoshi. 

    Link: http://www.nintendolife.com/news/2015/11/super_mario_maker_developers_discuss_the_difficulties_of_adding_in_yoshi

      

Glad they did though... having Yoshi expands your options by quite a bit

Hmm interesting that they address this.

I am hoping for Yoshi's inclusion in the game, cause he's a cool character!