How to add Services Projects to Health Score

Hi all 👋 newbie admin here with a question on the Health Score

Context:

My company offers professional services to our customers (i.e. training, managed services, etc) and when they sign a new contract for a service, they open a “Project” in Salesforce to track it until completion.

They then regularly update a “project status” field while it’s open to indicate how it's progressing with either a “Green”, “Yellow” or “Red” value. A customer can have either multiple, single or no projects at any given time. See the screenshot example for a single customer below who has multiple open and closed projects

My CS team would like me to add a new group to the Health Score for “professional services” with a metric that considers the “project status” of the open projects. 

The ask: I’d love to get some feedback on the best way to implement this 🙏

My thoughts on how to do this

1. I need to translate the categories of Green/Yellow/Red into a numerical score
   1. I think it could be Green = 100%, yellow = 50%, red = 0%
   2. Any completed projects or accounts with no projects would be left null, so the score would be NA
2. If multiple projects exist, I could take the average of them after the conversion

My concerns

1. What weighting should be applied? We currently already have 4 metric groups with 12 metrics in total
2. How should I handle multiple projects, does the existence of a “red” project override the fact there are also “green” ones?

Any other feedback, thoughts, or previous success stories on how to accomplish this?