NEC ECC: Change from main Option B to E due to uncertainty over effects of COVID-19

A Contract was awarded under NEC3 Option B in Dec 2019 with an Access Date in Feb 2020 (approx £1M value).
Construction is continuing, though it is being affected by the need to social distance, because usual suppliers are not open/operating at reduced capacity, third parties are unavailable etc.
An increasing number of early warnings are being notified in accordance with Clause 16.1, many of which will be CEs under Secondary Option X2.
The Contractor has suggested that the main Option could be changed from B to E in order to reduce the administrative burden.

I have not worked with Option E before, but wonder if:
a. changing main Option part-way through a contract is possible and/or advisable?
b. this would make much difference as he would still be entitled to CEs and, under Clause 63.15, these would be assessed using the SSCC?

Would you advise this as a credible approach to the problem?

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.