Figured it out, and I'm using cMaNGOS 3.3.5a.
>ChrClasses.dbc in server files unchanged
>ChrClasses.dbc in my patch-T.mpq has had all rows except for Warrior's deleted
>CharacterCreate.lua has had MAX_CLASSES_PER_RACE set to 1
>CharacterCreate.xml has had all ClassButtons except for 1 deleted, and ClassButton 1 aligned to x=0, y=-483
>shareddefines.h in src\game has had all of the entries except for Warrior under CLASSMASK_PLAYABLE deleted
I also renamed Warrior to Adventurer, replaced UI-CHARACTERCREATE.blp (i think thats the name, im away from the computer atm) with one that only holds a single custom icon where Warrior's was placed, and set the resource type in both ChrClasses.dbc files to 0, making them use mana.