I figured the bigger creatures were stronger so had more ablities, wanted to counter balance the -stat loss. Insanity isn't INT loss? Wrong there for me. So much to remember.
Darkvision over lowlight is fine that makes sense.
Do we really need a massive template or would a simple ECL of 0 be acceptable here with the majority of the work be the insanity table? Won't the flaws work just as well? This really doesn't seem to be that complex of a conversion as these critters have no real special bonus', no real special additions, just misfigured shells of the base critter.
Only bonus' are their 1d3 (seems right) modifications and the -4 to WIS, their Lawful (any). Considering these things are going nutty why not reduce the avg WIS by -4.
the class table above could be used to say what each critter is like in the caste for the DM to use.
Beetle juice: Fort save DC 12 (this adventure was very low level) or recieve -2 to BAB/DMG