9.G,
There are many Normal (all engines) procedures designers on these forums who will categorically verify that normal SIDs DO NOT consider engine failure. As OzExpat has stated, there's just too many variations between aircraft types to consider such a thing.
Your Remark -"At airfields where such performance is not guaranteed, a SID specific decision point procedure is developed" is very sound indeed. Being already commited to the SID and suffering engine failure is nightmare stuff.......unless a Performance Engineer worth his salt has indeed developed such a break-off point with subsequent OEI tracking. Many PEs do not, I do.
Your final remark -"It's pretty clear to me that as long as one follows the EOSID even being below MSA it's safe", yep, that's OK IF the PE has developed the EOSID ALL of the way to a Safe Climb Holding Area for further climb to MSA. As said before, many PEs do not, I do. Big "J" just gets you out to 30 miles (outside MSA coverage), and then you're on your own. (Big "J" has a much bigger litigation budget than I do).
No criticism of your excellent post, none at all, perhaps you fly for a reputable operator whose PEs take the care to ensure your safety all of the way to MSA, but sadly, many many pilots do not work for such companys.
Regards,
Old Smokey