With all respect, have you read everything above? The DEC-B tokens are actually what you are saying we need. You will use DEC to Buy DEC-B tokens these tokens will be soulbound and cannot be transferred until use. Once used, these DEC-B tokens will not return on the market but rather burned.
If you see the logic, this "technically" burns the initial used DEC.
Buy using DEC > Becomes DEC-B > USED DEC-B are burned.
This is EXACTLY what you're saying we need. The result of the used DEC-B will be reducing the amount of DEC circulating in the market.
However,
If the burning of the used DEC-B is before this post, then forget everything I've said and I apologize.