I am not trying **** in your corn flakes. Look at it this way. If you think 80% of your jobs can only be accessed with a 17 than your buying the right machine. If 80% of your jobs can be accessed with a 35 size, you bought the wrong machine. I had a CX17 on rent years ago for a couple weeks, handy little machine for digging lines into large pool where nothing else would fit. After its little stint, it was gone, because it is not cost effective to dig with it, when larger machines can do it faster. I have also had a 35 sized machine (IHI 35J). Did a ton of work with that machine, and learned the value of a mini ex. Went up to a 6 ton machine in 04 and that is where I stayed. Maybe this is the way to make the point if you have not done this already, go rent a 17. Go out somewhere are dig a utility trench a 100 feet long, dig footings for an average sized shop or garage. Then do the same with a 35 sized machine. If that doesn't convince you, nothing will.
I know what used trucks cost and I know what new trucks cost. I am just finishing up a flat bed that I put on a '20 Chevy 3500 CC 4X4 DRW I bought last week. I replaced the one I bought new in 06. They are expensive but it is the cost of doing business. It doesn't matter how good your half ton is, still has the towing capacity of a half ton. You do realize that you will be operating commercially? DOT doesn't care that you carry round bales with your half ton. They just want you legal when your pulling commercially. You will find yourself having to rent machines, perhaps bigger than the 17 machine. If you cant haul it yourself, your going to have to pay someone to haul it. It hasn't been mentioned yet, but you find yourself having to buy or rent a SSL or CTL at times. There are not a lot of mini ex only jobs in my experience.
I will say this again, if your picking a 17 because its all you can haul, not on the work that can be done with it, your making a mistake. You simply wont be able to compete and to do so you will be working for free or less than free. You make good points at what this stuff costs. That was the point brought across before, it takes money to get into this and it takes money to keep it going. Good used pickups can be found. The chance of having to put money into something (used pickup or excavator) is a sure thing. That is why you need to make money at this. Spending 5 times longer to get projects done, isn't going to be making money, you will be wasting your time and the customers time.
Either way, good luck.