Okay, so I know that I did this before with an idea of giving Piccolo a boost in power, but this time I am giving more of an outline of what the Dragon Ball staff could have done with Piccolo in Super. I know it's all just hypothetical and some is arguing from hindsight, but this is all just fun. Also just think of this as one of my disclaimers where I say I would have changed something from the series, just in a more filled out form.

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After the events of Battle of Gods, Piccolo sees just how far he is from the new enemies that are appearing. Despite knowing that he can't really catch up with Goku and Vegeta, he still decides to train to get stronger. While training he makes his weighted clothing heavier to the point that he can't use 90% of his power. Once the Resurrection of F saga comes around, Gohan then asks Piccolo to train him so the two of them can get stronger. After some time, while having a talk with Whis one day, Piccolo learns of an ancient power of the Namekians and decides to go visit New Namek to see what he can learn of this old form. Once there, Piccolo sees that the planet has finally been found by the reminder of Freeza's forces who are trying to get the Namekian Dragon Balls. Here the former Demon King finds two badly beaten Namekian warriors named Maima and Tsumuri who both tried to fight against Freeza's forces. Piccolo then fuses with them, reminiscent of Piccolo fusing with Nail. This gives Piccolo the power to wipe out the remaining Freeza forces that are there and now possess unlimited regeneration. Then while Piccolo spends time on Namek he looks for any and all information on the old Namekian form and in return trains the remaining Warrior type Namekians so that they can start defending themselves. Once Piccolo returns to Earth, he now knows what he has to do to reach the power of the new Namekian form. He then goes back to training Gohan so that they can work together to reach the new form (in Piccolo's case) and to regain the old form (in Gohan's case). Then right before the Universe Survival Arc, both Gohan and Piccolo can unlock these forms so that way they can better factor into the tournament. In the case of Piccolo he now has the "Red Eyed" Namekian form as his permanent base form. As the tournament goes on we see the power that this form has given him, making Piccolo stronger than Goku in his base form, equal to Goku in his normal Super Saiyan form, able to keep up with but is ultimately inferior to Super Saiyan 2, and is outclassed by Super Saiyan 3 and up. Later on after the tournament, Piccolo's new base form becomes equal with Goku's base form, able to keep up with but is ultimately inferior to Super Saiyan, and is outclassed by everything that 2 and above. After all of that at the end of the series, Piccolo has proved his worth now so that Whis has decided to train Piccolo now, since Goku and Vegeta have both risen to levels that they wouldn't need Whis to train them as much as they used to, so the angel would take Piccolo under his wing to have something for him to do while Beerus goes back to his naps. That way when they continue the series or make more Dragon Ball movies, it would make sure that Piccolo stays closer in power to Goku and Vegeta and for that to be believable. 

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There you go, there's something that could have been done for Piccolo to buff him. I drew some inspiration from the games (the fusion guys and the Red Eyed form) but hopefully this could have been believable for you guys. If you have something in mind for how you would have buffed Piccolo or some other character from the series, please let me know it the comments. Its always fun discussing some what ifs and what could have been.