lacerda70: This is a very interesting (to me) thread. Parsing statutes, parsing subservient regs, parsing non-binding (at law) but sometimes “authoritative” passages in the MPEP, and considering policy. A law professor’s dream exam question!!
This present post is directed to your reply of 2012.01.05 @ 15:21 (on my clock) only. I need time to consult the cited regs again, and consider the follow-on posts by Issac. bardenjc, and you. And I haven’t consulted - over even looked for - any on-point case law.
There were four persons, A, B, C, & D who contributed to patent-eligible subject matter
disclosed in the parent. Because only subject matter invented by A, B, and C was ever
claimed in the parent as filed, only A, B, and C were named inventors and only A, B, and C filed O&Ds. D was (lawfully) left off (bad decision ? good practice tip here?). On Constitutional grounds, I agree that named inventorship should, at the END of the (issue) day, correspond to actual/real/true inventorship for what is claimed in an issued patent. But what does that say about “inventor …
NAMED in the previously filed [parent] application” in §120?
Does it mean what it facially says, “named” (i.e the legal name simply appears on some formal papers in the file - formalistic in your words) in the prior application, or does it mean “one who’s name is on a formal paper in the file AND who is an inventor of the subject matter of at least one claim as filed in the parent and now sought to be claimed” ? It seems that UR question distills down to whether I should read 35 USC 120 according to its plain terms or as follows. #
§120: An application for patent for an invention [now sought to be claimed] disclosed in the manner provided by the first paragraph of section 112 of this title in an application previously filed in the United States, …which is filed by an inventor or inventors [of what is now sought to be claimed] named in the previously filed application shall have the same effect…#. Can one "apply for a patent" for an "invention" not claimed? Disclose yes, but apply for?
Reading the statute as I annotate it above, and I’m reading words into it, the priority claim in the OP scenario should fail. Resort to the Office’s regulation doesn’t really help me much. They are only regs (forget the MPEP, at best it binds Examiners, not DCs or the CAFC. SCOTUS? fugedaboutit). But IMO Rule 48(c), maybe (a) too, appears to come close, allowing me to add claims AND add an “inventor”, contemplating that claims - and importantly an INVENTOR - could be left off (or included) and later added (deleted) to accommodate addition (deletion) of claims in an already filed and Dec’d-up application. Isn’t that the scenario in the OP? .
Absent case law to the contrary, as your adversary in litigation, I’d argue for my annotated construction of §120 above. As a policy matter, D never manned-up and signed an O&D when the parent was filed. Why should D now be entitled to claim priority on the backs of A, B. & C who have no inventive connection whatsoever with what is now claimed (if they did, they would be inventors). D was never an inventor of record.
But OTOH I’d argue that, per the OP, the child was filed with proper inventorship - duplicate claims and duplicate inventors thereof - preserving continuity and the priority claim under §120, inventorship was later amended as required by claim amendments, in total conformity with Rule 48(c).
Lots of words, no conclusion, no concrete help 4 U.

Time to hit Lexis / Westlaw? #
I have an alternative to your tactic for dodging the issue - if there really is one - which putative issue I have never encountered. I’ve always named all inventors of all subject matter disclosed in the application - rarely have I had more than 4 inventors- then amended inventorship in the 1 out of 50+ cases where it was ever IMO plainly lawfully required. I don’t generally claim hats - invented by A, B and C - and shoes, invented by D - in the same application. And, in any event, my intent in naming all on filing was strategic - kick the inventorship can down the road to prosecution- never deceptive. #
Of course, your suggestion of filing at least one claim to which ALL putative inventors contributed - conception or reduction - works as well, or maybe better. If, despite all efforts, one just can’t draft such an "umbrella"claim, one likely has a unity-of-invention problem - claiming hats (invented by A, B and C) and shoes (invented by D) in the same application - and your client is too cheap to pay two sets of fees - or to pay that tiny fee for just one measly extra claim. In which case, IMHO, they get what they deserve - continuity fails.