Dragons can be an mob (agressive to every faction) who will spawn rarely in large caves in the Grey Mountains.
They will spawn rare and respawning like gollum.
There will be Cold-Drakes and Fire-Drakes they will have 50/50 chance to spawn.
Fire-Drakes would breath fire that will work like balrog's whip. It will have the same lenght than the balrog whip but it will have 3block wide not 1 (as the balrog whip does). Cooldown for the breath will be 10second so when a Fire-Drake is targeting you and not atacking ,or getting atacked will not do the atack.
Cold-Drakes would breath snow and make iceblocks that maybe could u get stuck(around 3-5 blocks per 1 breath) snow in touch with an npc or a player will do forodwaith frost dmg but staying in the breath of snow would get you a total of 3hearths of dmg. It would have the range same as the Fire-Drake but the breath will have 3 seconds, it can be stoped with an atack. The cooldown will be the same as for Fire-Drake and will have the same atack stopping mechanic.
Look of the Dragons------------
The drakes will be shorter than a balrog (1block shorter) but they will be longer with the 4blocks longer than the balrog. They will have long tails that will be 2 block tall. Large dragon scales agresive eyes as uruks (red for fire-drakes, blue-white for Cold-drakes) the cold-drake will be the color of ice of forodwaith,and the Fire-Drake will be the color of utumno fire level brick. Upon getting atacked they will sleep with a large breathing sound(to aware the player of the drake being there) when a player looks at them they will stop sleeping and will make a large dragon style the sound of a dwarf charging.
The Drakes will have 3 parts of the body the tail,torso,head. When a player would fight the dragon he needs to shoot the drake with a Bow that will have at least 150% Dmg. To acctualy make dmg to the dragon they need to shot 2 times in the same part of the body tail ,torso or head to get rid of the scales, bows,cbows with 200% dmg will take 1 shot to take off the scales. Upon taking the scales off the player must atack only the part that they taked the scales off to make dmg. The dragon will have 15armor points in that spot when the scales got removed. Only bows can remove the scales, soo rhun and mordor guys no bombs. Its best to use a Bow agains the Drake.
200 hp points (100hearths)
4dmg claw, 7dmg bite, 4 staying in the fire breath and burn dmg (fire drake), 8 for staying in the cold drake breath,
armor 15 unscaled part of the body, infinite for scaled part of the body
Heads (other for fire drake and other for cold drake),
Scales, but if u unscale the whole dragon u would get only 5 with unscaling 2 parts 15 and for 1 24, Fire-drake scale wil be other than a cold-drake scale
Scales and their uses---------
Scales will be used to create armor
Fire scale armor
it will be the same as mithril armor but it would have bad durability
The attributes of the full set will be immunity to fire (only works with full set). It would be repaired with fire scales
Ice scale armor
It will be the same as fire scale (the same protection,durability),
but the attributes would be blocking arrows (like galvorn) without getting durability destroyed, works only with full set. Repaired with Ice scale
Upon killing the drake (fire and cold) you will get an achievment called "The pets of Morgoth"
Morgoth's Dragons would be dead and these would be on no ones side.
If You want to play a dragon mod look into Ice and Fire because Mevans said these take LOTS of Coding to do.
Also All of the Drakes Would be in Angband or in The Northern Parts of Middle Earth.
Cold-drakes are canon, but I don't personally think they should breathe ice, and I don't think there should be fire-breathers. I'm less-inclined than usual to immediately dismiss this idea, since it's fairly concrete in my opinion; plus, if they'd be wingless, I'd assume they'd be easier to add.
I don't think they should drop scales, or if they do, you shouldn't craft armour with them. Perhaps they could drop their teeth? When Scatha was killed by Fram, his teeth were taken and sent to the Dwarves as an insult, so it would be a neat little reference. Perhaps killing a Drake could award you a dragon-scale shield?
The achievement for killing one's name should probably be changed. (While being able to find them sleeping might be too similar to Ice & Fire, along with several other aspects of this suggestion, it would be cool if awaking them would earn the achievement "Never Laugh at Live Dragons". Killing them should also award an achievement, of course.)
Cold-drakes could also spawn in caves in Forodwaith, or in the Forodwaith mountains. I'd say that these ones should be called the Cold-drakes, while others that would spawn in the Grey Mountains would just be Drakes. Perhaps the Drakes could spawn in different colours (grey, red, orange, etc)? Cold-drakes could maybe also have the same frost-effect on hitting that Ice mobs in Utumno do (they should also uncommonly spawn in the Ice level, and perhaps normal Drakes could spawn in the lower ones.). They might have to have a slightly less-powerful melee attack to make up for this.
EDIT: They could also have names and speechbanks, since Dragons were pretty intelligent. Perhaps the head-trophy they drop could have the "belonged to [dragon]" as other mob-drops?
There's still a good chance that this suggestion isn't concrete or original enough to be taken seriously, but in the case it is, feel free to use these ideas.
Honestly, this idea is great. Everything you wrote out for it is fantastic. All of your ideas for stats, attacks, and looks are very fascinating as well as very detailed. They make sense but this whole idea would be a bit odd. Smaug was the last Great Dragon of Middle-Earth which means the other dragons who are possibly around are lesser. The Dragons of Morgoth have a high chance of being extinct with oly lesser offspring still around. For location Withered Heath, Grey Mountains, or Erebor would be great areas. But two of them would not work since Smaug was slain so there would be no dragons in Erebor. Scatha was slain way before Smaug so the Grey Mountains wouldnt be a feasable choice either. The Withered Heath would be the only possible area for fire-drakes at least. (Even though Scatha *a cold drake* was in the Grey Mountains) But it is a rather small biome for boss spawning. Cold-drakes in Forodwaith would make sense but it would have to be farther off around near Utumno or somewhere far away. It would probably be a bit difficult to code a way to make dragons vulnerable in one area (like a soft spot) and not vulnerable in other areas. I do not know though because I am not that great a coding. To go along with what I said earlier about lesser dragons, there have been many generations between the Great Dragons of Morgoth and the dragons of today in the Third Age. As Smaug was the last of the GREAT Dragons, the others are lesser which means weaker and probably slower. This idea would be up for the question "Is it worth it?"
IUf dragons were ever implemented a large majority of them would have to be cold drakes, also they should be relatively small, smaug himself was about 20 meters in length(although estimates vary even from Tolkien's own illustrations), so i would say 10 to 12 meters on average, perhaps very, very rarely you could find a fire drake of 15 meters, or maybe there could be a special boss fire drake of 15 meters who is the biggest drgon after Smaug died, there was a non canon character in BFME2 that was the king of dragons after smaug's death.
As for what dragons should look like
In this depiction by Tolkien himself we can see that dragons in ME most closely resemble overgrown winged crocodiles.