At the time, Project Zomboid is based in the first year or two of a survivor (as long as I can see), but some communities are showing us that there's more to do when you can survive more than you expected, when you get experience playing this game, you know how to avoid zombies, farming, raid places and defend your bases (that it's a hard task alone, but a bit easier playing with a group), then the game should approach to a real way of thinking of an human being.
Are we really just leaving everything, and lost all our civilizated way of thinking in a zombie apocalypse? No, not really, maybe we could get more like a cold blood killer, but in the end, civilization is everything for an human, and trying to reconstruct at least a part of it, it's a need of it, for example, as we can see in The Walking Dead, apocalypse wasn't the end of all, a lot of small villages as Hilltop or Alexandria survived and tried to get civilization back again in some way.
That's a part about what I'm suggesting, thinking more like a survivor in all the social and order needs, in a small village it's obvious that you're going to be surrounded by walls, trying to avoid zeds, with walls, windows are not a problem anymore, you need to be comfortable, as the population as well, you're not going to live in a small colony afraid of broken windows if you have a wall around you.
There's a lot of needs in a colony, smiths (if the ammo isn't enough), glass workers, medics, builders, some politician trying to keep all the survivors togheter, and other stuff like that.
That could be like 3 - 4 years after apocalypse, when people understand that the government is totally down and the only persons that can keep society up are themselves.
I'm going too long at this point giving this explanation some ways of thinking of a survivor, but it's true, and this also could be an addition for the NPC in the future, make them more like a person trying to survive, but also with needs of social and order, not just killing machines.
Maybe if the glass system is too complex, it could be reduced, like using a pot, fill it with sand and use a campfire or a kitchen stove to compress all the crystal fragments, then pour it in a metal base or something, idk, but there's the point, thinking further from just the first few years.