Unless Kid is going to pull out some adv haki game, this is base Luffy w/o everything, but just basic haki, all over again.
Restricted this way, characters won't get past the Veterans and Tobi Roppo. They essentially lack the necessary AP and defensive skills, just like anyone else who's not a prime Ogre/Oni or a peak human guy like Garp or Whitebeard in base.
Imagine Kid just with body hardening against Full Zoan Ulti, Hybrid P1, heat Glaive Oven, gigantic Genie Daifuku... Those guys are plenty powerful.
On a regular most characters simply cap at that kinda lvl without DF abilities of their own, advanced haki types, body enhancements or being extraordinary physical specimen.