The pandora layout is a hack. Its a crux when you do the same thing when you dont have to.
wb: Why so cryptic, whats wrong with the US international diactric-symbols? And why not all of them?
The french will look for their letters on number row, because thats where they are used to finding them. Big and small versals with shift makes sense too, albeit isnt standard. All of which is only possible while maintaining more important things (US shiftrow symbols) by having a language-layer key.
US-International has only grave, tilde, acute, umlaut and circumflex. I have all of those, in the same spot as US-International (` ~ ' ") except for circumflex, because Meta+^ is already taken for Shift+F6. Unless of course you map to the "real" US-International, which makes ` ~ ' " ^ all dead keys, with no option to get just the symbol except by adding a space after the dead diacritic.
Of course you can always use my layout and set your keyboard layout to US-International, which means Right Alt (R2) becomes AltGr and you get ÅØÆ at AltGr+WLZ, and « » ¬ ¶ ç ¡ ² ³ at AltGr+[ ] \ ; , 1 2 3 and so on. Could be practical if you are already familiar with US-International; in particular, for Spanish US-International is quite good since it has áéíóúñ easy to remember at AltGr+aeioun.
The French who expect to find AZERTY with éèà on the number row are screwed anyway, also in comradekingu's proposal, because we have QWERTY, not AZERTY the number row is misaligned, which is a big problem if it contains letters (imagine the QWERTY row shifted one position to the right w.r.t. the ASDF row). Perhaps you can expect French people to blindly swap AZ and QW and put M at L+1, but you can't expect them to blindly remember all of the AZERTY number row symbols, AltGr+symbols and punctuation symbols, which are completely different than on US-QWERTY.
No, I think it makes much more sense for French people to adjust to US-QWERTY, as long as they can type àèé reasonably efficiently (frequently used letters) and çùâêîôûäëïöü in some way (it doesn't have to be a single thumb press for those letters, but preferably something faster than a three-thumb-press Compose sequence).