Perhaps this would work better as a Planeswalker in a spawn-token filled environment?
Regarding the Ninjas, one of the biproducts of Jund being so ramp heavy in Rise of Eldrazi is that Blue and White had to pick up some of the slack as the attackers (the Blue-White leveller deck). Similarly, we'll need to give blue a slightly more aggressive slant here. I am thinking of using the Ninjas, as well as some Detain / Unblockable / Curiosity effects to give these decks a way of pushing through damage (along with the usual suite of fliers). I particularly like Mistblade Shinobi here, with the presence of so many tokens.
Maybe even a couple black Ninjas could work here too. I think different blocking dynamics can work so long as they are not too overlapped on the color pie.
I like the Overgrown Battlement ramp plan. Do we have other useful walls that could play an interesting role?
Gatewarden gives us triple duty: multicolor, proliferates, Defender.
Structure is starting to come together...