The ABA, last I checked (which was a while ago), had a booklet on what "of counsel" means, and the of counsel attorney can be a K-1 partner getting guaranteed payments, a W-2 employee, or a sole proprietor with payments reported on a 1099-MISC. If a sole proprietor AND he or she no longer has any capital account or trailing interest in receivables, in theory they could have their own plan, since the 414(m)(5) and (o) proposed regs (which would have prevented) are currently a dead letter. If they still have a capital account or interest in receivables of even $1, then 414(m)(2)(A) would require aggregation.