Well, let's see how I'd make Black Mage! Sure, I'mma use the full 12 buttons, but I feel it's necessary.

Black Mage will only get 1000 MP and 1000 TP.

1. Blizzard Same as ever. Costs TP though. 200 potency.

2. Fire Same as ever. Costs MP. 200 potency.

3. Thunder Same as ever. 100 potency with 50 potency per tic for 18s.

4. Thunder II Same as ever. 50 potency with 50 potency per tic for 12s.

5. Transpose Same as ever.

6. Fire II Same as ever. Switches to Blizzard II in Umbral Ice... and makes that a target AoE. Both are 100 potency.

7. Scathe Saaaaaaaaaaaaame. 150 potency.

8. Fire III/Blizzard III Same as ever. Both are 250 potency.

9. Enochian Same as ever. Similar to PvP, this ability will be modified by which form you're using. Astral Fire causing Fire IV, and Umbral Ice causing Blizzard IV. Both Fire and Blizzard IV are 300 potency.

10. Flare Same as ever, but like in PvP, switches to Freeze when in Umbral Ice. Both use their respective resource, and Flare has 300 base potency, and Freeze has 100 base potency with Bind effect. Flare increases potency by 100 for every 200 MP is spent. Same for Freeze but with TP.

11. Foul Saaaaaaaame. 700 potency. A free damage booster every 30s.

12. Rites of Rosetta Same as ever... wait. That never existed. That's because Fire IV builds up a new resource, Astral Glyphs. These Astral Glyphs build up to 12, and once they do, they allow the usage of Rites of Rosetta. Upon doing so, you gain higher damage and you gain the following abilities, replacing certain others:

Origins of Flare: Flare, but now with bigger damage and Supperations as a debuff. No more MP cost, but uses 2 Glyphs instead. Base potency 2000.

Origins of Freeze: Freeze, but now with bigger damage and a damage area, kinda like Shadow Flare. No more TP cost, but uses 2 Glyphs instead. Potency 1500.

Astral Foul: A whopping 1200 potency that utterly wrecks everything.

Umbral Foul: A whopping 800 potency that.... increases magic vulnerability. Sweet!

You lose Glyphs every 10s that you don't use them after activating Rites of Rosetta, and you regain a glyph with each cast of Fire IV.

Trait: I cast the spells that makes the peoples fall down! Astral Fire increases damage by 25%, 50% and 100% for all Fire spells upon each stack obtained. Refreshes TP.

Trait: Healed and healthy forever! Umbral Ice causes an increase in MP refresh rate, and a slight regen. This refresh/regen is 10%/5%, 20%/10%, 40%/20% with each stack gained.

The design is essentially an exageration of what BLM is now, with a little Risk/Reward with Rites of Rosetta.