No the address starts with a 1, multisig addresses would start with a 3. I thought about this as well, but more in an abstract way. Since OP IMHO think cooperation is the way to go, multisig would be the way to enforce that on the final step. That would require some serious branching though. And since multisig isnt easy to use currently I doubt it will end there.

Currently like S4VV4S said we should be looking for a password or passphrase.

Each riddle in the past had some sort of noise with it. The 1st step had plenty of letters/numbers left. The morsecode had some parts at the end that have not been used, all the way to the minecraft world which had a portal to "the end" which had no reason.

I think we should be aware that this step might as well have some form of noise or distraction. The "obvious" cat each of us saw was one of the distractions IMHO. Same with the matrix leads and everything else that just has somehow the numbers 7 and 51 in it. I was thinking about the german movie 23 yesterday. Its about the hacker karl koch and how he got more and more crazy (or come to close to the illuminati however you want to see it). He saw the 23 everywhere. There is a part in the movie where he and a friend just drive around town and everything is Illuminati. There is a 23 and a 5 (2+3 = 5) and VW (V is the roman 5 and W is the 23th letter in the alphabet) and the cigarette brand camel has a pyramid in its logo, etc. etc. After I watched the movie for the first time I saw the 23 everywhere. So be carefull with that, you might be chasing rabbits.

The part about bit and sha beeing shifts of eachother might be relevant, not sure.