Now, with bitcoin there is again and when we talk $10, 20, 100 million worth... All bets are off....people have sent entire teams of heavily armed people to kill for a lot less. Not to be over-paranoid but I think Wall St. firms who think they can simply use the office safe and building security for 45,000 coins are making a mistake.
I think I see the issue you're trying to raise.
You're saying Wall Street will want to treat this just like an ordinary security which of course it can't be because this asset is a currency.
You'll need banking expertise to secure the asset but the instrument itself can be left out on someone's desk.
Are you thinking that there are going to be bonds or something with private keys printed on them? This could be the cause of the potential scalability issue you mentioned?
If that's the case, you really don't need to do that. The private key doesn't need to be printed and you could still have claim to a tranche of Bitcoins.