. Since it is not active or playing the curation game, it should have a penalty instead of the 50% it gets say, 25% as if it is voting late or very early.

I wouldn't go for any fixed numbers. Instead the current vesting rewards could be redirected from SP holders to 'savings'.
That way the interest on 'savings' will be dinamic. More funds is kept on 'savings' less is the interest rate.
Everybody is withdrawing and selling, those who don't - start to get some extraordinary high interest.