Sure, although there are implementation issues because of the incentive for straw man purchasing. Are you aware of any jurisdictions where low-income purchasers are given additional exemptions?

I would think it would be easier to use transfer payments (like SNAP) to ensure that the exemption is not used for the benefit of non-low-income individuals.

Alternatively, you can have a prepaid or postpaid refundable VAT, where individuals can get their VAT refunded (up to a limit) based on income.