What bigger issue were you thinking of? The odds will be good that whatever you come up with, there will be a "bigger" one that you're not thinking of.
It's turtles all the way down. Choose your turtle carefully.
Rule of law not being followed through abuse of law enforcement and prosecutorial discretion, violations of rights and protections, conflicting laws. Hard to find a bigger issue than the very foundation of the system being ignored.
This isn't going to change that very much. Now they'll pull you out for field sobriety tests and blood draws just like with the smell of alcohol.
The discretion I was talking about is where they can choose to charge one person and not another. This leads to implicit and explicit bias. It also undermines the integrity of the system. Why should I trust a system that can ruin my life with a charge and let a similar offense go with someone else? Equal protection and application of the law should be required.
Police love it. A smell is invisible and leaves no record; it's impossible for a defendant to dispute that an officer thought they "detected the smell of marijuana".