The problem is in a declining market, who is going to want to take on a half finished house? Builders can't find buyers for their own stuff, much less someone else's. They don't know what short cuts the original builder took, and sometimes there is some non-disclosed reason the builder is walking--seeing settlement issues already, big delays on some needed components, maybe even title issues. Lot of risk to someone coming behind the original builder.
There will very likely be a much bigger discount on an SCA basis for the as-is value than simply pro-rating the cost to finish, even including entrepreneurial profit. For someone to take it on, they will do their own calculations on likely time to complete, carrying costs, likely value at completion (if not sold before then), and a pretty large risk factor.
I would call a couple local builders and casually ask them what percent discount they'd need to want to tackle such a beast in today's market.
And if your market is declining, I would certainly make that known in the report for the as-completed values. Do they want a value as-completed today? Or value as completed at estimated date of being finished? Those would be different in a declining market of course.