About tipping the scales: In my view, as someone who is a criminal defense attorney who litigates cases every day, yes. But I imagine that is not the view of a well meaning principled privacy advocate.

Before 180 days, you need a warrant. After 180 days, you need a (d) order. Can the defense can get it using a 18 U.S. Code § 2703(d) order? In my view, the answer is no. The statute specifically refers to a "governmental entity" being able to seek the order. I don't believe that includes criminal defendants.

See: https://www.law.cornell.edu/uscode/text/18/2703

"A court order for disclosure under subsection (b) or (c) may be issued by any court that is a court of competent jurisdiction and shall issue only if the governmental entity offers specific and articulable facts showing that there are reasonable grounds to believe that the contents of a wire or electronic communication, or the records or other information sought, are relevant and material to an ongoing criminal investigation."