I know. The thing is, there are two methods of dynamic lights: actually having a light source at the position of the player, which will lag, or just making it a visual effect, which people don't like for some reason because it's just a cheap cop-out.
Well, then a visual effect could be used, since it isn't as laggy.
Prismarine can't get slab or stair variants unless Mojang fixes how they look underwater, seeing as they are encouraged underwater blocks.... yeah.
As for iron/gold/whatever well we need them to be still convertible back to their original resource, so frankly that seems hard to do without adding nugget versions of everything, which sounds not worth it.
As for higher rez skins, I would totally enjoy that so long as the community didn't abuse it.
Iron/Gold/Whatever slabs could be simply able to be crafted back into blocks. That way, it doesn't require any new items.
Minecraft isn't really medieval, but it is clearly timeless.
Guns would not be a good idea, especially because we already have bows.
Redstone is kinda ambiguous if it's tech or magic, A simple resource pack can completely change that.
A good idea for any suggestion is for something that could be in any era if resource packed.
Binoculars wouldn't be good, a telescope would though because they've had those for ages.
Actually, there IS a way to give them an unique niche:
If they're 1-handed in design (Since somehow it's possible to use bows and swords a tthe same time, that would be needed to prevent them from looking weird), they could be made to work as a secondary weapon. For example, what if, rathe rthan being standalone, they were designed to be used with swords?
That alone opens up many opportunities, since it makes sense for guns to not use the same firing mechanics as bows (Not necessary "Point and shoot", but, for starters, they could modify their accuracy instead of their damage if charged), so it makes sense to be able to fire them while moving at full speed; and that opens up possible enchantments, such as making it so that hitting mobs with the guns gives the Strength effect to the player (Which means that the player would be encouraged to use it to soften up crowds before using the sword).
In fact, the fact that guns are the most varied ones would open up many possibities, such as using pellets or whole slugs, 1-handed or 2-handed (Doesn't work in the Dual Wielding slot) guns, slow-firing or rapid-firing (I'm not specifically saying "machine guns", althrough a single automatic weapon would be probabily acceptable if there weren't shotgun-like weapons, In the sense of "Fires a spread of damaging projectiles", because they would compete and the latter wouldn't involve adding unique mechanics).
Why not a revolver? A six-shooter that is slow to reload and expensive to craft, but would pack a punch. And because of all the moving parts, it would be unenchantable.
Actually, that would be a good way to add them, since that means that the issue of the only gun suggestions that are at least somewhat liked being useless in SSP because of overspecialization in single-target damage would be avoided (Namely, most use crafting recipes for reloading and have to be reloaded after each shot. Making them fire several times before reloading would be an at least make them actually useful). It is also helped by the fact that revolving cilinders were actually around since the XVI century.
The only thing I don't like is not being able to enchant them, but, considering that it would be difficult to figure out an unique enchantment for guns, I guess that wouldn't be much of an issue.
Minecraft has a medieval theme and guns would destroy that.
It doesn't really have a medieval theme (A few counterpoints would be jukeboxes, everything related to Redstone, which could be used in a gun as an electric primer analogue; and a limitless amount of building styles). It's real theme is the ability to build anything you want. Guns (Only if modular) could help with that (Not to mention that there were medieval guns).
Definitely not...and while we're at it, let's also throw the emerald armor and guns into the same NO fire.
Guns could probabily be added. It's merely difficult to find a convincing way to do that, as either it results in a Bow with more damage (Which would be acceptable, but too bland), a complex set of parts only used to make guns (Which COULD be used to make them customizable), an OP mess, an complete set of garbage that is less useful than the Bow and is also more expensive (Which is the result of most Musket suggestions), or a mix of all of them.
Meanwhile, Emerald tools can't even claim to BE a good idea, since there's already enough tool tiers, so, unless Emerald tools were to be unique tools (Similarily to Shears), the result would be pointless redundancy.
They would have a chance to spawn each night and randomly land on any exposed block. Upon landing, they spawn Meteorite Stone (A new variation on cobblestone similar to Granite, Diorite and Andesite) and ores. The ores would use a chance system similar to how ores are spawned on worldgen, making all ores renewable but coal, which wouldn't spawn in meteorites (As it would be strange because coal is of organic origin and because it is already renewable by either using charcoal or killing wither skeletons).
Meteorites would have varying sizes, from 1-block small bits to boulders made out of 32 blocks.
They would also have 2 gamerules concerning them:
SpawnMeteorite (True by default), which causes them to spawn.
MeteoriteGriefing (True by default), which causes them to break blocks on impact. If false, meteorite blocks spawn on terraiin without damaging it.
In minecraft, lava is so hot that when you toss any sort of iron into it it sublimates directly into steam. You can test this directly in-game by tossing said items into lava and then jumping in to try picking it back up.
And yet it doesn't melt buckets, so I'd simply call it Realism<Fun.
Perhaps remove the new biomes in 1.7 as well as the new stone variants in 1.8? They're all useless. Plus, not only are the new stone blocks ugly as heck, but the new biomes broke seeds that I've been using since 1.2.5 and there are no mods for 1.2.1-1.6.4 world gen/world types for 1.7.10 or 1.8/1.9. The new stone blocks are an eyesore and they don't look like stone at all, they look like some sort of shiny gravel. And speaking of gravel, the new gravel texture from 1.3.1 and onwards is terrible compared to the old one, the old one at least LOOKED like gravel, the new one looks like a grey sponge. Also, maybe possibly Mojang should embrace Forge and make it their official modding API like they did with Bukkit for servers?
Pre-1.7 worldgen was really boring, and the new stone blocks are only ugly to some people, not everyone.
Rabbits should be better as a food source. Rather than simply buffing their meat, they should be able to breed and mature faster than other animals and spawn more than one rabbit (1-3 or so) each time they breed, meaning that they would be a fast source of meat.
Maybe they'd give you an item, like a Tormented Soul. Yeah, that sounds AWESOME!!! It could be used to craft armor. Now this is more like a mod. Time to go put this in the mod suggestion area - wait there is already a ghost mod. Darn.
Or make it drop an item that does something actually unique. Such as using it to make dye that makes blocks see-through.