In this report on accelerating the settlement cycle DTCC explains that a t+1 cycle could reduce the often unpredictable instrument-specific risks as well as order execution risks while still allowing the clearing house to net orders. However, in a t+0 scenario, the authors point out that netting would not be feasible and orders would need to be pre-funded. In the table below, they also point out that institutional investors would need a comprehensive overhaul to their order submission strategies.
I would have liked to seen this discussion taken a few steps further. For example, whether or not retail investors would also face similar workflow complications. Perhaps, as most retail traders do not buy securities on margin (correct me if I'm wrong), they would not have as many points of failure in their order execution strategies. On the other hand, retail traders tend to have less capital strength than larger traders, maybe at some point that would become a factor in t+0.