Would it be consistent for a libertarian to get a job at a government regulatory agency if that libertarian tried to not enforce the regulations whenever possible?
Oh yeah. This is war, and every war has its saboteurs.
The danger is always that you’re sending the signal that the job itself (of tax-funded authority) has validity and value.
This is a war of information first and foremost.
Also, even as a saboteur, you still end up doing evil.
I’ve thought about something similar, namely the morality and utility of becoming a government cop. Sure, you’d be able to do some good but you most certainly wouldn’t be able to avoid busting non-criminals altogether, and you’d be sending false signals, as said above.