Manga-wise, he'd probably replace Kuririn seeing as how he lacks anything either Goku or #18 can't cover skill-wise. Since Gohan wasn't PSSB tier at the start and only became such through adapting to his opponents, only Goku, Vegeta and Freeza are going to offer a significant boost, and not enough to compete with Jiren. He can solo the rest of the competition though and with infinite stamina and candy beam, their teamwork would be ineffective. Jiren remains the only obstacle so it'd come down to whether or not he has the skillz to win. I'd say with Roshi's Ultra Instinct GAINZ, he'd be able to win after a long fight due to superior skill.
Anime-wise, he'd get stomped since there's far more characters stronger than SSB Goku such as Hakai GAINZ Toppo, Kefla, Peak Hit, Anilasa and Dyspo's Super Light Speed mode in terms of speed/reactions. Absorbing 4-5 SSB tiers and gaining Taiyoken x100 isn't going to help unless he can also access Kaioken x20. If he can, he'd probably solo. If not, he'd get stomped by anyone of Anilasa's level or above.
