Hi, I'm Jared and this is my first post. Glad to finally join a forum after a lifelong fascination with Godzilla and kaiju!
I think the best results for special effects in Godzilla films can come from combining practical effects and CGI - have a suit with miniatures, an animatronic, a motion capture-suit, and of course a Godzilla fully rendered in CGI. By having all four techniques at their disposal, an FX crew could choose which is optimal for any given scene, and if done right, could acheive a uniformity/consistency of believable effects rather than the hit-or-miss FX work we're used to.
For example, CGI works a hell of a lot better for a closeup of Godzilla's foot coming down - the airport scene in GODZILLA (2014) proved this. But as soon as we get the big reveal to Godzilla's face a few moments later, it reeks of noticeably fake CGI - in which case a suit or animatronic could have done the trick.
All water scenes should be done CGI, because a) you can't miniaturize water, and it often ends up looking like a big bathtub, and b) the big pool was extremely dangerous for the suit actors.
Some of the work in the Millennium films used a mix of CGI and practical decently, but never to a degree that seemed fluid. The Gamera Trilogy did a pretty great job, considering the budget, particularly when Legion burrows into the ground...first time I saw it, I had to rewind to check if it was the suit or CGI (and it proved to be the latter of course). Get similar talent, give them a much bigger budget and more time, and Toho could finally live up to their potential for modern tokusatsu effects. That is, if they ever make Godzilla movies again...