I can help you with some of that. I have a couple creatures that do some of what you want, and I can throw out a few raws that might be helpful as reference. Even though they don't really do exactly what you want.
First off I had created a creature with copper and iron equivalent scales. I set it up to be used as leather, but I imagine it's possible to set it up as a metal instead. And even failing that it should be possible to just make a custom reaction to melt it into whatever metal you want.
Pretty much what both of these do is select the scale materiel, and then apply the properties of the metal, directly copy pasted from the metal raws. Then it just tells the game it's a kind of leather. it should be possible to set them as a metal instead the same way.
[SELECT_MATERIAL:SCALE]
[MATERIAL_VALUE:2]
[ITEMS_ARMOR]
[ITEMS_HARD]
[ITEMS_METAL]
[ITEMS_BARRED]
[ITEMS_SCALED]
[IMPACT_YIELD:245000]
[IMPACT_FRACTURE:770000]
[IMPACT_STRAIN_AT_YIELD:175]
[COMPRESSIVE_YIELD:245000]
[COMPRESSIVE_FRACTURE:770000]
[COMPRESSIVE_STRAIN_AT_YIELD:175] 140
[TENSILE_YIELD:70000]
[TENSILE_FRACTURE:220000]
[TENSILE_STRAIN_AT_YIELD:58] 120
[TORSION_YIELD:70000]
[TORSION_FRACTURE:220000]
[TORSION_STRAIN_AT_YIELD:145]
[SHEAR_YIELD:70000]
[SHEAR_FRACTURE:220000]
[SHEAR_STRAIN_AT_YIELD:145] 48
[BENDING_YIELD:70000]
[BENDING_FRACTURE:220000]
[BENDING_STRAIN_AT_YIELD:58]
[MAX_EDGE:5000]
[LEATHER][ITEMS_LEATHER]
[SELECT_MATERIAL:SCALE]
[MATERIAL_VALUE:3]
[ITEMS_ARMOR]
[ITEMS_HARD]
[ITEMS_METAL]
[ITEMS_BARRED]
[ITEMS_SCALED]
[IMPACT_YIELD:542500]
[IMPACT_FRACTURE:1085000]
[IMPACT_STRAIN_AT_YIELD:319]
[COMPRESSIVE_YIELD:542500]
[COMPRESSIVE_FRACTURE:1085000]
[COMPRESSIVE_STRAIN_AT_YIELD:319]
[TENSILE_YIELD:155000]
[TENSILE_FRACTURE:310000]
[TENSILE_STRAIN_AT_YIELD:73]
[TORSION_YIELD:155000]
[TORSION_FRACTURE:310000]
[TORSION_STRAIN_AT_YIELD:189]
[SHEAR_YIELD:155000]
[SHEAR_FRACTURE:310000]
[SHEAR_STRAIN_AT_YIELD:189]
[BENDING_YIELD:155000]
[BENDING_FRACTURE:310000]
[BENDING_STRAIN_AT_YIELD:73]
[MAX_EDGE:5000]
[LEATHER][ITEMS_LEATHER]
I defined those within the creature, which I think will work within caste level. But you might wanna make sure before you go to far with it.
I also created a few D&D dragons of my own, but only the black, white and green, and their breath are a bit overpowered, but they are functional.
[USE_MATERIAL_TEMPLATE:DRAGON_POISON:CREATURE_EXTRACT_TEMPLATE]
[STATE_NAME:ALL_SOLID:frozen green dragon venomd]
[STATE_ADJ:ALL_SOLID:frozen green dragon acid]
[STATE_NAME:LIQUID:green dragon venom]
[STATE_ADJ:LIQUID:green dragon venom]
[STATE_NAME:GAS:green dragon venom]
[STATE_ADJ:GAS:green dragon venom]
[PREFIX:NONE]
[STATE_COLOR:GAS:GREEN]
[STATE_COLOR:LIQUID:GREEN]
[SYNDROME]
[SYN_NAME:green dragon poisoning]
[SYN_AFFECTED_CLASS:GENERAL_POISON]
[SYN_IMMUNE_CREATURE:DRAGON_GREEN:ALL]
[SYN_CONTACT]
[CE_NAUSEA:SEV:40:PROB:90:BP:BY_CATEGORY:GUTS:VASCULAR_ONLY:SIZE_DILUTES:START:1:PEAK:500:END:2000]
[CE_IMPAIR_FUNCTION:SEV:100:PROB:40:BP:BY_CATEGORY:EYE:VASCULAR_ONLY:SIZE_DILUTES:START:1:PEAK:500:END:6000]
[CE_IMPAIR_FUNCTION:SEV:100:PROB:25:BP:BY_CATEGORY:HEART:VASCULAR_ONLY:SIZE_DILUTES:START:2000:PEAK:5000:END:99000]
[CE_DIZZINESS:SEV:100:PROB:25:VASCULAR_ONLY:SIZE_DILUTES:START:2000:PEAK:5000:END:99000]
[CE_FEVER:SEV:100:PROB:50:VASCULAR_ONLY:SIZE_DILUTES:START:2000:PEAK:5000:END:99000]
[USE_MATERIAL_TEMPLATE:DRAGON_ACID:CREATURE_EXTRACT_TEMPLATE]
[STATE_NAME:ALL_SOLID:frozen black dragon acid]
[STATE_ADJ:ALL_SOLID:frozen black dragon acid]
[STATE_NAME:LIQUID:black dragon acid]
[STATE_ADJ:LIQUID:black dragon acid]
[STATE_NAME:GAS:black dragon acid]
[STATE_ADJ:GAS:black dragon acid]
[PREFIX:NONE]
[STATE_COLOR:GAS:BLACK]
[STATE_COLOR:LIQUID:BLACK]
[SYNDROME]
[SYN_NAME:dragon acid]
[SYN_AFFECTED_CLASS:GENERAL_POISON]
[SYN_IMMUNE_CREATURE:DRAGON_BLACK:ALL]
[SYN_CONTACT]
[CE_BLEEDING:SEV:5:PROB:25:LOCALIZED:VASCULAR_ONLY:SIZE_DILUTES:START:1:PEAK:2:END:30]
[CE_BLISTERS:SEV:300:PROB:100:LOCALIZED:VASCULAR_ONLY:SIZE_DILUTES:START:1:PEAK:2:END:100]
[CE_PAIN:SEV:300:PROB:100:LOCALIZED:VASCULAR_ONLY:SIZE_DILUTES:START:1:PEAK:2:END:100]
EDIT:Removed some specific immunity creatures that don't exist in vanilla DF from the green and black syndromes
The white dragon was the first one I did, and it is really disorganized and garbage, I don't even remember exactly how it works.. But it does work, and I have a 'if it ain't broke, don't fix it' policy. It's spagetticode is included just for the sake of completeness.
[USE_MATERIAL_TEMPLATE:DRAGON_ICE:COLDBREATH_TEMPLATE]
[STATE_NAME:ALL_SOLID:frozen white dragon gas]
[STATE_ADJ:ALL_SOLID:frozen white dragon gas]
[STATE_NAME:LIQUID:condensed white dragon gas]
[STATE_ADJ:LIQUID:condensed white dragon gas]
[STATE_NAME:GAS:white dragon gas]
[STATE_ADJ:GAS:white dragon gas]
[PREFIX:NONE]
[STATE_COLOR:GAS:WHITE]
[STATE_COLOR:LIQUID:WHITE]
[MATERIAL_TEMPLATE:COLDBREATH_TEMPLATE]
[STATE_COLOR:ALL_SOLID:WHITE]
[STATE_NAME:ALL_SOLID:dragonbreath]
[STATE_ADJ:ALL_SOLID:dragonbreath]
[STATE_COLOR:LIQUID:WHITE]
[STATE_NAME:LIQUID:dragonbreath]
[STATE_ADJ:LIQUID:dragonbreath]
[STATE_COLOR:GAS:WHITE]
[STATE_NAME:GAS:dragonbreath]
[STATE_ADJ:GAS:dragonbreath]
[DISPLAY_COLOR:3:0:1]
[MATERIAL_VALUE:1]
[SPEC_HEAT:NONE]
[IGNITE_POINT:20000]
[MELTING_POINT:5000]
[BOILING_POINT:15000]
[HEATDAM_POINT:NONE]
[COLDDAM_POINT:NONE]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:1500]
[LIQUID_DENSITY:1500]
[MOLAR_MASS:20000]
[IMPACT_YIELD:50000]
[IMPACT_FRACTURE:50000]
[IMPACT_ELASTICITY:10000]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:100]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:100]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:100]
[SHEAR_YIELD:10600]
[SHEAR_FRACTURE:10600]
[SHEAR_ELASTICITY:5000]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:100]
[MAX_EDGE:100]
[ABSORPTION:6000]
[LIQUID_MISC_CREATURE]
Blue I was waiting on something to better simulate lightning, but it might be possible to do with multiple breath attacks. Which if I recall correctly causes them both to fire at once. Perhaps one could simulate lightning with a undirected gas that only stuns, the stunning effect from the soundwave, and a second solid or liquid glob breath that is rather heavy to simulate the force of a direct strike, with a strong local blistering effect. If it is heavy enough to actually propel opponents back from the force that's even better.
A sleep syndrome is incredibly easy. There is a drowsiness syndrome that does exactly what you want. Throw that on a vapor breath and it's golden.
Run away sadly does not appear to currently be possible. Or possible in the immediate future.
A slowing syndrome would probably be accomplished in a roundabout way currently with a stun effect. In the next version's expansion to syndromes it will simply be a matter of an agility debuff I imagine.
A weakening syndrome probably needs to wait til the next version. But will likely just be a strength debuff.
A paralysis syndrome already exists. And was actually the poison effect that has been in the game the longest. GCS use it if you want a reference. You can probably just change their syndrome from injected to contact and make it a vapor breath like the sleep breath.
Might just have to copy and paste body tags for the tiamat caste problem and define the body from the caste level for each other caste, even if all but the tiamat one are identical. It's dirty, but I don't know any other way to do it.
For the crystallization you may be able to add a reaction class to your breath materials when you define them, and then just have you reaction look for that reaction class. But I don't know if you can define reaction classes from within a creature or not, if you can't you would probably have to make the materiel separate. And depending on how the breath is used, it may not be possible to collect the materiel, unless maybe you give them a gland or something that a butcher can harvest from a corpse.
I rambled, but hopefully there's something of use to you in all that. D&D dragons was something I was always interested in, but lacked the patience to give a full effort at.