This would be quite cool
I am not sure how many fields you need from your Project object, but you could build an aggregate model on Tasks to get the count by WhatId. Salesforce does allow filtering by the What.Type…so you could filter for the count of Tasks for only your Project object. For your other Project fields you could use model lookups to pull in the other values. I don’t think the model lookup fields would be sortable.
This seems like a feature that could only be implemented client side since that record count only happens when the model is loaded from Salesforce. It would be a nice feature.