I would like to speak from experience and respectfully disagree with your opinion that ballet training prevents development of good technique for folkloric dance. Even a grounded and earthy baladi or raqs assaya is easily destroyed by poor body line and posture.

My first instructor was trained heavily in ballet before she transitioned to belly dance and yet her performances were strong, powerful, grounded (when appropriate - i.e. not during a classic Oriental) and had the necessary "folk" element. Taking ballet doesn't mean that your arabesques will suddenly become higher or that you will 'sterilize' your dance - it will help you improve arm posture so you avoid the "chicken wing" look, keep a beautiful effortless lift in your chest, have a better sense of head positioning (very important) and add a lovely extension to your posing and body placement.

I have taken some ballet and it did improve my dancing all around - both the glamorized and baladi versions.