This functionality already exists in 6.3.x and will be rolled into the 7.x LTS soon. On tasks there is an option to continue on error.
Also, if you take a look at this patching postrecently done it will show an example of pulling history of executions. Mine looks generally at Job executions but you can refer to the instance history and report back on status of tasks. Something like this could look retroactively at the workflow and group errors if desired.