I did this subclass a while back and it never sat quite well with me. It's too much without feeling like anything distinct. After the Amber article, though, I think I cracked them. I think they must even be a full class now, so let's have them work like Thieves without any thief stuff. Correction, they can get Sneak Attack damage but only with bit-ass knitting needles.
Suitmation
A BLT has the power to infuse all the magic of Amber into a particular pattern, instead of activating its normal abilities. There are 6 such magical patterns known only to the tailor elite and there may exist more. A BLT's Suits are obviously bespoke and only fit the individual they were tailored for, usually the BLT herself although they can work for anyone. Making one of these Suits costs 1000g/level but all BLTs begin play with 1 Suit that fits only them. Suits cannot be re-tailored, but must be built from scratch. Suits found in the world as treasure will only fit BLTs. Each level the advance a BLT will learn a new Pattern until they know them all. At level 7 they can work with the DM to create a new magical Pattern using what they've learned, and at level 8 (as high as they can advance) they can open a Shop, take on an Apprentice (level 1 BLT), and can make Suits for half price.
Awakening a Suit with Amber activates one of the Suit's magic powers until the suit takes damage. Even 1HP of damage or catching a thread on a nail undoes the magic. Suits that are damaged can be repaired without interrupting normal reprieve benefits during a ten minute rest. Raw Amber can activate 1 power at a time, Polished Amber can activate 2 at a time, Pure Amber can activate all 3. Which abilities are activated is determined by the BLT at time of activation. Suits can't benefit from more than 1 piece of Amber at a time.
Normal Amber abilities are not activated when Amber is expended BUT you should always roll the appropriate dice anyway to see if you get a Summon. In the event of a Summon the Prismystic instead appears dressed in their own version of the Suit in question with all its attendant abilities.
Patterns
Beetle
Throw- A successful attack throws the enemy your Strength in feet unless they are a larger size than you.
Thick Shell- 3 pt AC Bonus
Mandibles- Attacks as a magic axe, can clear brush for 5' per round.
Cat
On Your Feet- Immune to fall damage
Purr- Pacify/mesmerize one intelligent enemy for as long as you keep it up
Bad Luck- Enemies take a penalty equal to your Level for all saving throws if they can see you
Frog
Hop- Leap your Dexterity in feet per round
Climb- Adhere to sheer surfaces, climbing without a check until your Suit wears out.
Amphibious- Hold your breath for up to 10 minutes, full speed while swimming
Hare
Burrow- Spend 1 round to hide in earth, can tunnel an additional 7' each round.
Outrun- You gain free movement while running, able to swoop around the battlefield without worrying about positioning or attacks of opportunity or whatever, +10' to your encounter movement speed.
Snowbunny- Immune to cold, invisible in arctic climates/white background
Mouse
Hickory Dickory- Allow an ally to rewind their entire turn (movement and spell or attack or whatever Melissa did when it was her turn) and do it differently. Spell slots are not regained.
Churchmouse- Move Silently 6/6
"Blind"- Has darkvision, immune to Illusions and Charms.
Raven
Flight- As the Amber power.
Sneak- Hide in Shadows 6/6
Nevermore- Enemies who miss you cannot target you with an attack again until your Suit wears out.