>The old "toor" *is* a duplicate root account and instantly makes it
>twice as easy (statistically speaking) to guess a uid==0 password.

 Only if they have distinct  passwords. Duh.

as for root's shell being an innovation: BSD has done so since,
uh, at least  4.1, iirc.

BSD is BSD.  Those who want a sysV clone know where to find it.

(otoh, if you want to run 6th Edition vax binaries on a Unibus vax,
 I've done one pdp-11 AME under vms. Gimme a vax and pay the power bills...)