The proposed definition of valid is too broad. Suspended / revoked licenses don't have legal effect
The proposed language, "having legal effect" would mean that not only expired driver licenses are not valid, but that suspended and revoked driver licenses also cannot be used for identification purpose. The election official will not necessarily be able to tell whether or not the person presenting a suspended or revoked driver license is using a valid ID.
This language could be legally challenged. Any person convicted of a traffic violation could challenge the suspension / revocation of their driver's license on the ground that loss of voting rights is a cruel and unusual punishment for speeding.