I have a desire to get an expandable solar system started.
I am pretty insistent that the system be off grid capable.
I agree completely. The grid is old, dependent on subsidies, and increasingly unreliable. And in the event of economic and/or social collapse, it'll be completely useless. However, perhaps you should reconsider the grid-tie portion. If it's off-grid capable, why maintain a grid connection at all? The grid is like training wheels. If you still think you need it, your system is not truly off-grid capable.
Basically I would want to start with a 1 KW system, grid tied, battery back up that could be expanded with additional panels to up to a 6 KW system, with the capability of accepting energy from a generator, and watermill or windmill or the kids new stationary pedal bike charger I built.
It sounds like you need to establish your actual requirements. Sure you can start with 1kW and expand it, but it will be cheaper and easier to start with the minimum of what you actually need. In my experience, you're going to need *at least* 1-2kW of solar and 1kW of something counter-cyclical to solar -- wind is good, though water is great if you have it. If you only use solar, you'll need *at least* 3kW and a bigger battery bank. These figures are dependent upon you having high-efficiency appliances and lighting and NO electrically-powered heat (incl. hot water, dryer, oven, etc.).
The problems I think lie in the distances.
Distances can be solved with two methods -- up-sizing your wiring or up-converting your voltage, or both. My system is 24V. That's what my wind turbine puts out and what I designed my battery bank for. The solar accomodates that too, by down-converting from 48V at the charge controller. I like 24V because many things natively operate at that voltage, including a wide selection of down-converters to 12V. I have no problems getting 24V some 150' to the opposite side of my house with virtually no voltage drop. The wire isn't terribly expensive, but it's not cheap. I don't recall what guage I used, but it's whatever was recommended by the wire guage charts. If you want to use a cheaper guage wire, design your system to be 48V. However, understand that some of your other components may be more expensive.
I had a fairly large local solar company come out and give me an estimate, which they rescinded a month later. They said they no longer wanted anything to do with battery based grid tie systems, and were pulling all their contracts.
That's typical. It's cheaper and easier for them to install grid-tie-only systems. And because of tax rebates, they have plenty of business doing only those. I personally think it's insane to do a grid-tie system, as there is no benefit from the expense. You're still dependent on the grid, but now a very expensive producer.
You'll be better off doing it yourself. I wouldn't trust most of them to touch my system anyway. I started off using a contractor because the wind turbine was only available through a dealer-installer. They screwed everything up. Reversed polarity, no disconnects, no fuses or lightning protection, inappropriate grounding, etc. I had to redo everything. It's best just to do it yourself from the beginning -- as long as you do plenty of research and ensure you're being safe.