Some financial service providers (i.e. those who do NOT buy low sell high) might try to move into the custodial market. Assessing the risk there is beyond my pay grade I don't know how smart that'd be ... but we can observe it's not common. If that did happen clients could use that provider's IT system to do trading and voila since all data is at one provider, some kinds of reconciliation is easier. In short, market consolidation.

There's tactical steps too that can partially overcome the independent IT systems, say, getting the custodian to send data realtime, sending it realtime on the trader's behalf to the recon entity ... I'm not sure what custodial service provides think about that ... presumably they would if they could probably hampered by their own IT systems like the rest of us.

The final approach is what appears immediately above: traders and custodians --- generally any set of business entities N who need to compose data --- publish to a virtual shared DB. I'm gonna read the white papers and follow-up afterwards.