There you go.

{table=head]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[/table]

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.