There you go.
| Level | Base Attack<br>Bonus | Fort Save | Ref Save | Will Save | Special | Spells per Day |
|---|
| 1st | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 2nd | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 3rd | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 4th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 5th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 6th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 7th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 8th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 9th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
| 10th | +x | +x | +x | +x | Class Ability | +1 level of existing spellcasting class |
Although I have to ask... why is there a spellcasting progression? This seems like a rogue-type class... not to mention the fact that you can't speak means you'd have to take Silent Spell to be able to cast without breaking your mime oath.
I'd replace the special mime check with a Perform: Mime skill check, and take away the ability to mime magic items. That just seems open to all kinds of broken madness. Instead, have your mime items bypass various forms of DR as your class level increases. Maybe give a scaling enchantment value for weapons and armor.