I kinda could see Mei somehow a trans-girl eventually or at least a non-binary/gender-fluid as well after all he isn't much like as guy aside of his genitals perhaps but his gender is pretty ambiguous since the original manga.

I actually could as well, though I much rather imagine him as a guy, cisgender or not, in a mlm relationship ^^

Yeah I still like him better as a cute soft femguy and still being a dude in love with the other and being properly loved back too They're an amazing couple either way. Also I think he won't stay a cute guy always but maybe over time will take a very handsome and stern wild-like mature figure properly fitted as being the mate of Gabu and so will grew up to stand on his own and along him on hunting times, maybe helping on taking over large preys as pride-vain deers which need some help of a surprise attack for Mei from behind or on side with his horns hitting hard enough to make the deer stumble and so being properly finished on a throat attack by the wolf while Mei still might hit hard on their heads too with his hoofs as it's needed for getting some large preys reserves for winter time in the forest. (Also he might have also helped to surprise and terrorize stunned poacher-hunters who were looking for kill Gabu yet were totally unnaware of the proximity of the goat nearby them and... well they actually have a harder time by the surprise with no time to use the arm on him as well, he mades it being unable to reach for the hunters and well Gabu goes to help him as well on fighting back and expelling the hunter away too pretty much scared by the sudden unexpected outcome of a jointed chase by a big feroucious wolf and a also very fearsome goat along him.)

Oh, I thought of Mei as a hunting helper too before! Though I was thinking more as a helper for little things, not quite the teamwork you desriced ;3
Maybe to distract other animals. But I think either way he'll definitely come a long way from the scene in the movie, where he disagrees with Gabu killing the mice. When living with Gabu, he'll probably appreciate his wolf boyfriend keeping a good and healthy eating habit. Maybe he's even ok with Gabu killing other goats because it's his favourite food? ^^

I think he'll go for hunting mostly smaller to middle preys as well eating some vegetables as wolves like all canines are actually omnivores yet though leaning more into carnivores too, so both him and Mei might share eating some fruits, seeds, and roots as well in common. However from time on time, Gabu goes for hunting some deers under the agreement of not hunting neither the doe along with fawn or fawn alone itself, but could hunt lonely does as well even more the vain-pridefull old bucks so then both got to arrange a way of succesfull hunting, where Gabu will do most of the chasing of them and got the harder time evading the fightback of the adult male deer with his antlers and hoofs, but Gabu will kept the buck distracted and tired on to fight and run away so couldn't listen Mei running alongside hidden in parallel until it's too late and the goat gets hitting hard in the stomach, rear area or even the chest side of the buck making him to stumble so Gabu could finish faster going straight to his neck and throat side to suffocate him. Mei also learn to use the hoofs to hit on the knees of the deer if failing to make the surprise killing attack to make as well him to stumble and well also jumping high to hit them on the forehead hardly too to knock into mercyfull uncouncioness while Gabu finish them.

The hunting times are rarer as they are harder and Gabu still gets most of injuring for fighting, chasing and killing the deer most of himself as well still also defending Mei for his shorter size of the larger herbivore, at least early on when they haven't got yet well builded the strategy of hunting together that way. Mei grew up somewhat wolf-like eventhough a goat as stealthy, larger-slender athletic-muscular, getting a coarse and not so cute hair style better fitted for ambush and an active running daily-life, also getting more active into night as well adjusting his eye-sight and well got some nice fighting set of horns and hooves for both fighting and killing purposes as well.

However I don't think Gabu ever got to hunt another goat again, and perhaps I envision them going back after a while to the original area where they lived for a lasting visit for Mei's old grandma before she dies so he could thell her how well and wholesome happy he actually is and that she shouldn't be afraid about him anymore. Therefore they also met along his friends Mii and Tappu, and well finally got all settled that Mei couldn't return for Mii's feelings toward him and that should accept Tappu's runing into her for a big while about it, and they finally accept the match with help of Gabu and Mei. However they might get some trouble as though some wolves, including Giro the leader, passed on the avalanche, the second-in-command Barry got on the leader position and alongside the former she-wolf mate of Giro go into revenge of both Gabu and Mei once they knew they're back into their former area. Still at the end they win over them, with some help of Mei's friends and the comical minor-level wolves pair, Zach & Beach, who aren't so much bad either way and get along well with Gabu and his new friends eventually learning how to addapt (and also not being well-treated by Barry or Giro's widow either way) and help to recover Mei's grandma who is taking hostage for a tricky surrendering of the goat and wolf; however they weren't counting on Mei's friends provoking a new avalanche and well, both Gabu and Mei fight back on the main villains, the wolf against Barry and the goat against the she-wolf ending up them in a rather bloddy hardcore fierce time, which takes totally by surprise on the female wolf btw after noticing how well trained and deadly those hooves and horns now are fitted on a wolf-like goat which totally gets her demise in full surprise, terror. angryness and awe that couldn't make enough to make a proper stand on him after all.

Finally as both the leaders are killed by Gabu and Mei and most of the pack got killed in the new avalanche, Zack and Beach choose to surrender to follow Gabu and Mei as their new leaders, and well as they couldn't risk on returning back their original place as maybe some wolves will survive again or take the former domain of the clan there, Gabu and Mei lead all the group including the goats - even Mei's grandma - and the wolves into the Emerald forest, where they no longer need to care on having a hard time being all one-family along. Thus Gabu finds better proper hunting companions when needed for larger preys and all got a safer healthy place to live along, specially very rewarding for old Mei's grandma lasting days before a natural demise, and Mii and Tappu rise a family on a very safer place keeped by that lovely odd special couple of guys.

Wow, that's one heck of a story

Sorry, I envisioned which maybe could have happened in the future with the characters and make sense on they adding more others into their group they might lead over time and makes sense to bring back more positive characters for them in the past (as Mei's friends and close-family) or were neutral-cute (as the comic-relief pair of Zach & Beach which were much less harmfull than any other wolves there). I wanted to have Mei's grandma getting into recent later clashes against that old "wise" bigot ram leader of the herd of goats actually thinking into defending his grandson decisions and his survival, as she denyies to ever rest untill have news of him. (He passes away for being killed while she got abducted after learning of Gabu & Mei's secret return and meeting with her by the wolves.) Also wanted to expand the silent she-wolf mate of Giro and well got Mei to show up how great he has evolved to make a stand on his own even for other predators.

I personally saw it more as a simple friendship movie, but I can see how some could interpret it this way to I guess.