"You are mistaken on federal practice. A number of federal district courts (not all) allow any bar member to join,"
I was uncertain on this, so I looked into this in response to a query in another thread. Every single D.C. I looked at in a brief sample required licensure in the state in which the D.C. was located, or, on occasion, a neighboring state. I did not find a single D.C. in my limited search would allow for "any bar member" to join. I highly recommend doing a thorough search prior to accepting this advice. Short version- I belive this to be wrong, unless you have a very generous definition of "a number."
I do agree that there are other federal bars, including the Supreme Court and the COAs that you can get admitted to by bootstrapping, say, a CalBar admittance- but you should also note that CalBar has really, really, really bad reciprocity.