Minotaurs can pick up weapons of their fallen comrades. The equipment list in the stat block does not indicate the weapons are large.
So the weapons are definitely not large? Halflings can use them?
PC Kobolds have just been too much on the outside, exposed to regular daylight. Their darkvision has simply been lost to them. It's a little like pigmentation for human skin...
Most of my games would be more likely to feature kobold delvers than kobold farmers. Maybe I'm wacky that way. And what if your campaign is set in the side of a mountain riddled with caverns? What if the party always travels by night? What if the kobold wears a poncho, a straw hat, and sunglasses? It's a contrived explanation. We know why it's contrived. We know it has nothing to do with logic and everything to do with justifying a game construct. Kobolds lack darkvision because they are PCs.
Sure, every kobold could be darkblind, spent too much time in the sun, an obscure subspecies, and so forth. And they can go adventuring with an albino human, a one-legged dwarf, a halfling with pituitary gigantism, and a pixie who lost their wings tragically in a game of tag.
Essentially, not giving kobolds darkvision says, "This is too powerful or causes problems." Which amounts to, "There is not very much good play experience to be gained from a group in which one party member has darkvision... having an actual, real kobold in a party could not possibly be interesting enough to justify figuring out some way to balance it."
I don't think the way to handle monstrous PCs is to turn the party into adventurers from the Land of Misfit Toys.