It will be gargantuan. Depending on the models you're comparing, the top of the head of a same scale RX-78 might approach the neckline of the Nu Gundam or its shoulders will barely clear the Nu's waist.
I wonder how stable it will be. The old PGs with backpacks just do not stand on their own: The Wing Zero uses its feathers to support it, and the Aile Strike comes with a stand. Overall the funnels aren't as heavy as either, but the weight is very concentrated.