I'm not trying to say that changing Godzilla's posture somehow damages the character, only that in doing so there are trade-offs. There is certainly plenty of room to adjust Godzilla's appearance and for Godzilla to still be instantly identifiable.
Take a gander at this side view of Godzilla Junior.
While Junior does have some limited grappling ability the effective range is drastically reduced by the angle of his torso. With this type of posture we would need to trade Godzilla's classic fighting style for one largely based on the abilities the Tyrannosaurus Rex & similiarly built dinosaurs (aside from tail strikes and the atomic ray). An example, Godzilla with this posture would not be able to rip off MechaGodzilla's head as Godzilla did in GvMG.
Not that all this is a bad thing, it's just part of a trade off.