Hi, Richard.
My model has everything that is not labor, maintenance, SaaS, and depreciation rolling through the Other Cost Pools object. A fair amount of cost, some of it tied to vendors and some of it not. At this point, my model is not really dependent on vendors to drive costs anywhere.
As it relates to a Vendor object, I'm just stepping into that mine field as well. I've created a Supplier object, and I have cost going into it so that I can generate a total vendor cost, but it stops there. I don't allocate cost out of that object. So, I'm allocating some costs out of the Cost Source object at 200%, once to go up the Cost model, and once to go over to the Supplier object. I'm not sure if this is the best approach, but it's working for me for now. Whether or not I eventually integrate the Supplier object into my Cost model to drive costs up the model, time will tell. But for now, it gives me vendor reporting ability without having to spend a ton of time rebuilding my model.