It certainly opens a can of worms though, I can see the democrats pushing for 16 (Scotland's done the same and it's further pushed the conservatives out of power there).
It'll also be far easier to fight the GOP proposal in court as there will be people who are actively disenfranchised by raising the age, but it's not clear that existing voters could have standing to sue if we enfranchise younger people.
But i'm not sure all of the things in the 14th amendment are necessarily criminal. I can't see how it's be a crime to give comfort to someone like Enrique Tarrio, but doing so disqualifies anyone who's previously taken an oath to uphold the constitution. How would that be enforced?
I look forward to seeing clarence thomas tie himself up in knots over that.