Hi,
I think thats a good idea.
I don't know enough about PV installations to say exactly where you should run the provisions, but there are some pretty picky rules about where the disconnects have to be relative to the service entry. It may be difficult to run some of these cables later. You should allow space for the inverter and disconnect panels. If you want battery backup for your grid tie system (so you still have power in a power failure), then you should provide for a place to put the batteries and charge controller.
I would have a PV installer come over and layout good places for everything, and then do the wiring provisions with that layout in mind. If you look at the Outback site under their GVFX grid tie inverter, or the Xantrex site under their XW grid tie inverter, you can get an idea whats involved in a system.

I would also put in provisions for solar water heating, which is likely to have a better payback, and would definitely benefit from having plumbing and controller wiring provisions, as well as space for a solar heated water storage tank near your regular hot water heater.

Gary

Where are you building? Here in cent fl where ac is the primary concern, the only sensible way to heat water is with a heat recovery unit on your ac. Free hot water plus lower ac operating cost. Much cheaper and simpler than solar. Solar hot water heating in Florida is a waste of money..

We are building in central VA where summer temps run in the 90's and winter in the 20's...mixed humid climate. Initially, we had rejected solar hot water because we are using geothermal and thought that we would use that for pre-heating the water. However, since my original post, we have come to realize that our needs are geared more toward A/C than heating, as we will be using a woodstove for much of the cold weather here. In that case, we would not be running the GT...only circulating the air. So, now we are planning on solar hot water. DH had a guy come by to size it up and it looks like a "go".

I don't get into recommending HRU's except here in Florida where I live...since we use AC 9 months of the year. That makes it a no-brainer to use a HRU on the AC to provide free hot water most of the year (and increase AC efficiency). Good luck with your system!