I've been following this thread all along. It seems to me the simple
answer
at the very beginning is that the "safety pilot" must be legal to fly
the
airplane, period.

Your simple answer is wrong. The safety pilot only need posess a private
(or better) pilot
certificate with category and class ratings and a medical. He is not
required
to meet the specific pilot in command requirements (currency, BFR,
HP/complex
endorsements) etc... unless he is specifically serving in that role.

Here are the only two rules that apply to safety pilot qualifications:

91.109
(b) No person may operate a civil aircraft in simulated instrument flight
unless -
(1) The other control seat is occupied by a safety pilot who possesses at
least a private
pilot certificate with category and class ratings appropriate to the
aircraft being flown.

61.3(c)
(1) Except as provided for in paragraph (c)(2) of this section, a person
may not act as pilot in command or in any
other capacity as a required pilot flight crewmember of an aircraft,
under a certificate issued to that person under
this part, unless that person has a current and appropriate medical
certificate...

Nowhere does it say he has to be "qualified to fly the plane." His role
is to provide the
see-and-avoid vigilance that the hooded pilot can not provide.

Well, Ron(s), on at least two occasions while acting as safety pilot I
have assumed control of the aircraft. First, when the hooded pilot blew an
approach and started wandering diagonally across the airport and second when
I had to take evasive action to avoid another aircraft.
But those aside, you cited 91.109(b)(1) above. I don't know any other
way to interpret that other than being qualified for "...the aircraft being
flown." I contend that with my SEL certificate, I may NOT act as safety
pilot in a twin-engine aircraft, nor may I act as safety pilot for an
aircraft on floats. On the other hand, the fact that I have zero time in a
V-35 does not mean I can't go there.
I think you are playing with semantics. Qualified does not mean "checked
out in."