I had posted some ideas here a while back discussing potential ways to bring Earthlings back into contention in a major way. For those who haven't seen them, here is "Self Dominion" a form that unleashes the user's potential power by taking control of their cells.
https://dragonball.fandom.com/f/p/4400000000000238044/r/4400000000001348709
And my version of Grand Kaio-ken, a multiplier than takes the user to thousands of times their limits through... unconventional means...
https://dragonball.fandom.com/f/p/4400000000000238950
I have been stewing on these ideas and finally brought them to life. First let's start with the Ultimate Turtle Style: Gamera. The famous kaiju Gamera exists in Dragon Ball and is a pet of sorts to Roshi. Gamera has a laundry list of abilities that can be transferred to the Turtle School students namely Krillin. The Gamera form is a evolution of Krillin's Selflessness State or No Ego Zone, forming a protective "shell" around his body that absorbs damage. His compact ki would allow him to perform explosive feats of strength far beyond his limit. However, the form is taxing to maintain so it is primarily defensive.
Next is the Kizukin technique which loosely translates to "Scarred Muscle". This technique is a result of an Earthling (DBH's Note in this example) conditioning their body to sustain heavy damage. It is similar to making their entire body a callus, numbing to pain. This would allow them to utilize the Kaio-ken more freely, pushing themselves to the breaking point without losing concentration or control of the dangerous power of the technique. However, this doesn't negate the side effects of reckless use of the Kaio-ken, just the pain.
Lastly, there is the Saku technique which translates to "bloom". Similar to Naruto's Creation Rebirth, this technique allows the user to accelerate the growth of their cells to utilize their power. It also has the added effect of healing minor wounds and halving train time. This comes at the cost of premature aging and shortening the user's lifespan.
