NEC's ECI clauses are primarily designed to be used where there is: uncertainty about the scope; a requirement for significant collaboration amongst stakeholders; a need for joint ownership of risk and decision making; and where risks are difficult to quantify. It is only intended to be used with main Options C and E as it works on the basis shared risk and reward, and joint incentives to deliver the project within budget. Option A is essentially the least collaborative main Option as it pushes the most risk onto the Contractor and hence could work against the main objectives for using ECI.
This said, with careful thought there is no reason why ECI cannot work with Option A however the published ECI clauses would need amending to achieve this. You really need to think about what behaviours this approach could drive. For example is the Employer willing to incentivise the Contractor against performance against the Budget? If not then this won't encourage the Contractor to design or construction within Budget which could delay / compromise proceeding to Stage 2 and drive a behaviour where the Stage 2 price is driven down by the Employer during Stage 1 to fit budget which then increases the likelihood of compensation events driving it back up again in Stage 2. Sound familiar? Oh yes, that's how traditional procurements often played out which makes you question why you would do it in the first place? Is the Employer's main driver based on procurement constraints which mean if it was two contracts then they would both need to be subject to competition? If you did follow ECI with Option A using amended clauses, then it would delay getting started on the design until you'd negotiated the contract for Stage 1 and Stage 2, and potentially delay proceeding to Stage 2 as I've already mentioned. Fundamentally the Employer needs to define their objectives prior to the right contract strategy being developed.
This said, with careful thought there is no reason why ECI cannot work with Option A however the published ECI clauses would need amending to achieve this. You really need to think about what behaviours this approach could drive. For example is the Employer willing to incentivise the Contractor against performance against the Budget? If not then this won't encourage the Contractor to design or construction within Budget which could delay / compromise proceeding to Stage 2 and drive a behaviour where the Stage 2 price is driven down by the Employer during Stage 1 to fit budget which then increases the likelihood of compensation events driving it back up again in Stage 2. Sound familiar? Oh yes, that's how traditional procurements often played out which makes you question why you would do it in the first place? Is the Employer's main driver based on procurement constraints which mean if it was two contracts then they would both need to be subject to competition? If you did follow ECI with Option A using amended clauses, then it would delay getting started on the design until you'd negotiated the contract for Stage 1 and Stage 2, and potentially delay proceeding to Stage 2 as I've already mentioned. Fundamentally the Employer needs to define their objectives prior to the right contract strategy being developed.