That vagueness is actually in our favor if the D's draft "Bump Stock Ban" (now expanded to be a complete new, 125 page long AWB) bill passes at the Federal level. It gives solid grounds for a legal challenge, that the SC has upheld multiple times. See:
https://www.law.cornell.edu/wex/vagueness_doctrine
The claim would be on 5th & 14th Amendment grounds, entirely separate from any 2A claim.