| Zurai |
Do what the template tells you to do. Do not do what the template doesn't tell you to do.
The Skeletal Champion template does not tell you to change the creature's mental stats or to remove any special attacks or special abilities. So don't. A Skeletal Champion can cast spells if the base creature could (or if it takes levels in a spellcasting class after becoming a Skeletal Champion).
| The Thread Necromancer |
Do what the template tells you to do. Do not do what the template doesn't tell you to do.
The Skeletal Champion template does not tell you to change the creature's mental stats or to remove any special attacks or special abilities. So don't. A Skeletal Champion can cast spells if the base creature could (or if it takes levels in a spellcasting class after becoming a Skeletal Champion).
And it would be a CR 1 + Character Levels (i.e., a Skeletal Champion Wizard 5 would be CR 6).