That looks promising, though like olbriar, I question the deep cleaning of it. I'm also not a fan of the Weber style flavor bars in anything where I cook low and slow. If I render the fat out of a couple of pork butts it simply builds up on the bars as there isn't enough heat to flare them up, then you have to deep clean prior to any other cook. Aside from that, the griddle attachment looks cool, the pizza stone, meh, just toss any pizza stone on there, no need to pay extra for a Ninja one. If it fits, it will do the same thing. I think I'm using the 25 year old Pampered Chef one on my traeger and in my oven. Works perfect.
I like the convection action to keep the heat even, that's taking a nod from air fryers and combining with the easy control of propane.