It is possible to change the main Option but you would need to enter into a formal deed of variation for it to have effect.
The effects of CEs in Option E are different to Option B, when implemented an Option E CE only changes the forecast of total Defined Cost however the Contractor is paid the Defined Cost regardless as to whether or not there is a CE. Whilst this may reduce the administration burden from a cost point of view, you still need to manage CEs from a time point of view if the Option E contract is to state a Completion Date.
If both Parties understand the risks and have the deed drawn up professionally then there is no reason to advise against this approach. However, bear in mind that whatever change you make will apply from now until the Defects Certificate is issued which will likely be a considerable amount of time after the effects of COVID-19 have ceased to impact.
The effects of CEs in Option E are different to Option B, when implemented an Option E CE only changes the forecast of total Defined Cost however the Contractor is paid the Defined Cost regardless as to whether or not there is a CE. Whilst this may reduce the administration burden from a cost point of view, you still need to manage CEs from a time point of view if the Option E contract is to state a Completion Date.
If both Parties understand the risks and have the deed drawn up professionally then there is no reason to advise against this approach. However, bear in mind that whatever change you make will apply from now until the Defects Certificate is issued which will likely be a considerable amount of time after the effects of COVID-19 have ceased to impact.