I have just had a guest post published in Larvatusa Prodeo which suggests that it would be better to use an "Include by exception" approach to developing the climate action plan required to meet 2020 emission reduction targets. This plan might start with a base plan that uses the clean up electricity on its own to achieve the target and then modifies the base plan by adding other actions to the plan with the aim of reducing overall cost and/or giving a better result. The modification may include reducing the extent to which electricity would be cleaned up so that the 2020 target remains unchanged.
The big attraction of this approach is that it is much easier to understand than systems like CPRS that have started out as EXCLUDE by exception. The problem with CPRS is that by the time all the exclusions are included the system has become extremely complex and difficult to understand.