We get repeated requests for consulting projects. There are couple of experts in our firm. They have different expertise in different fields. We would like to choose for each project the expert who has the highest probability of success. But only the experts themselves know their qualifications for each of the projects. We would like to have some mechanism of allocating the projects to the experts so we will be able to make them report honestly us who has the best fit for each project.
Your Problem, Restated
This is somewhat of an X/Y problem. If I read your post with a critical eye, there's an unstated command-and-control assumption here that the organization must assign a specific resource to a project, but lacks the technical knowledge or insight to do so properly.
This is exactly why agile organizations advocate collective ownership and self-organizing teams. You don't have to become an agile shop, but may want to at least give agile teams, estimation, and resource management a try to address the problem at hand.
Experts Should Allocate Themselves
Rather than trying to fix a broken process, I'd recommend that you adopt the concept of self-organizing teams. Your subject-matter experts should be allocated to a team that collectively owns the resource-assignment process. They would be responsible for:
- Working with your sales and business analysis peoples to gather specifications for the project.
- Using their detailed knowledge of the specifications to define high-level work packages.
- Determining amongst themselves which of them (or which combination of them) would be best suited to address specific work packages.
- Reporting their work breakdowns and other conclusions to project leadership.
The organization would then support the team in coordinating these work packages with one another, and with the customer. This process embodies core agile principles, and works extremely well when you have qualified and engaged team members.
Note that for this process to work, the entire pool of SMEs would have to collectively own the planning and delivery process. Otherwise, you will simply end up with a sort of slapstick reverse-volunteerism where the SMEs or the organization pick out a scapegoat who is then "held accountable."
Holding involuntary parties accountable never works out well for anyone involved. Don't do that.
Delphi method could be used if you trust in the ability of your experts to self-assess. Ask each expert to recommend which of their peers (or themselves) are best suited to the project as described, and have them report back in confidence, rather than to the group. If there is consensus, move forward. If not, re-query with the narrowed choices.
This leaves open the possibility of the experts all choosing themselves, or everyone choosing someone else without the ability to narrow down the choices, but resource availability should also factor in and help to make a clear determination.