Instead of making him a perverted little gremlin
This is my problem with him as well. He comes with the burdens of being a kid character without the naturally endearing qualities which come from being a kid due to how self aware he's presented.
Going further with your Kid Zoro suggestion, I think Yahiko from Rurouni Kenshin is exactly what you're asking for. He was a headstrong brat who desired to be a great samurai just like his father before him. He grew steadily strong with each arc, and eventually inherited Kenshin's sakabato (reverse blade). His relationship with Kaoru was also much better, being a cross between unruly siblings and master/student, and less offputting than Momo's interactions with Nami, which only reduced to her as cushion for his lecherousness. It feels a little unfair for me to compare Momo to Yahiko, though, since the latter is a primary cast member who has some of the best development in the series, whereas Momo is just a supporting character for the Wano saga, even if he's an important one. But what I'm getting at is, Momo should be written a little more like a little boy. Heck, scenes showing him training with Zoro, developing his male interactions a bit, could go a long way. It would also show Zoro as more of a mentor, highlighting his maturation over his journey.
I still think it's possible in writing him as the unassuming kid and making it work, since Oda's intent was for Momo to be so far removed from his dad, even having a bald head to contrast with Oden's crazy flat-top.