1. A common standard
2. Global openness
Surely they can build their own walled garden, but I think they're missing the point with this. With a walled garden you're just taking 1/100000 of the HUGE pie, improving current financial processes but not coming up with new radical innovations. A simple payment/monetisation standard embedded in objects (IoT) would be an example of a bigger piece of pie.
IMO they should just push for an open standard and use private ledger contracts on top of Ethereum, but I doubt they'll go this way. Most likely they'll just fork and run with it.
A private blockchain (like the one the banking industry presumably would deploy) can do 1 of 1000000 possible applications for the technology, but a global and open blockchain could channel all under the same protocol (something like TCP/IP), maximising interoperation among player in several industries.
I'm just trying to reflect that these 9 big guys could be making a short-termed shortsightedness mistake trying to protect their business placing a fence. As Szabo said, it's the moment to be more open.
Nick Szabo: If banks want benefits of blockchains they must go permissionless
https://uk.news.yahoo.com/nick-szabo-banks-want-benefits-085...
"So they keep trying to re-inject points of control, and thus points of vulnerability, into blockchains, e.g. through 'permissioning'; but this nullifies their main benefits, which come from removing points of vulnerability."