SVP
Just a thought for you. I understand your reasoning, but consider that you are talking about putting 24,000 hours on your equipment if everything goes perfectly as planned. It will likely end up taking longer as there are always delays. You will have some machines pushing 30,000 hours by completion. In my experience, once past 15,000 hours, the size machines you are getting into will need major overhauls, with many repairs leading up to that time. The first year should go pretty well for the equipment, if the mechanics keep up on the small things and don't let problems grow. After the first year, there should be budget for spares to make up for machines down for various levels of service.
A note about the concern for resale value. The resale value of the fleet will be a tiny percentage of the operating cost over the time indicated. If you can gain even a small percentage improvement on operating costs, it will likely exceed the resale value, so even if you could not sell at the end, which I think is unlikely due to demand for machines worldwide, you would still be money ahead.
It sounds like there is more to it than that. If your relationship is with Volvo, as all your equipment choices reflect, then that is what you will use for hauling. I can understand that for financing reasons. I would still encourage you to upsize at least half of your excavators to 700 class machines. I once had the second 700 Volvo on the West coast in the US, and I can tell you it is a great performer, and will load nearly double what the 460 will, if equipped properly.
Sizing the fleet based on start up means you make money the first 30 minutes, and loose money the balance of the shift. I would rather loose a little at start up and have a matched fleet for the other 9.5 hours. With 20 trucks, and 1.5 minute load times, the whole spread can be loaded with just 3 machines in 10 minutes. That is less than the haul and return time, so they will be sitting waiting for the first trucks to return. 6 excavators will load them out quickly, but then they are gone in 5 minutes, and they wait another 10 for the trucks to come back. I still say the money would be better spent on more trucks.
I would recommend you start ordering replacement tires now, so you will have a stock of them by the time they are needed, as 29.5's are in high demand. Don't worry about having too many, as it won't happen.
Best of luck to you as you undertake this project. Please drop in and keep us updated on how it is going.
Stock
Remember, in the part of the world he is in, unlike yours and mine, labor is a small expense. Fuel, tires, GET, are the big ones. Saving on those costs will be better than saving on labor, though most recommendations will save that as well.