For the sake of this thread, Gremmy's outer space feat will NOT count as a creation feat, but a transportation feat.
www.fanverse.org
It's NEVER been anything other than a transportation feat, unless you want to keep trying to deal with the inherent contradiction of him being able to make galaxies when he needs at least one clone just to make a continent level meteor.
He's literally only done this to a guy who was his creation to begin with. If he could have done it to Kenpachi, he most certainly would have and yet he didn't. Luffy is stronger than Kenpachi in every way.
Yeah just a shame Gremmy's reality warping is shit compared to that spatial hax haki was able to resist so I see no reason it wouldn't. Especially as Bleach has a very similar system regarding hax and having much more reiatsu (haki in this case).
Again he couldn't do any of this shit against Kenpachi directly, so why is he going to be able to turn Luffy into shit when Luffy is even stronger?