Sounds like a golf course irrigation system. They use a single mainline that runs VERY large sprinklers one or two at a time. The valves are built into the head.

The only problem lies in your controlling of the valves. You are going to need to run wire the entire length of the main line to your last valve, not very cost effective to run the two most expensive parts of the system the longest, when lateral pipe is cheap.

Most larger residential, and commercial systems don't have just one manifold. I normally use one in the front of the home, and one in the rear, but have had as many as 8 on one clock.

If you are going to be running more than 1 lateral pipe side by side, it sometimes pays to just run wire and a main line, like if space is a problem while plowing pipe, or having to go under concrete or around objects like trees or fences.

You wouldn't really be time or money ahead by running a mainline completely around the perimeter. Just run it where you need it. Main line pipe is more expensive than lateral pipe, due to the pressure ratings it must have. You would want at least 125 lb rated pipe for your mainline, and really all you need for your laterals is 80 lb

Thank you for the good advice and for taking time to write detailed info. The reason for the main line idea was that we have concrete pathways and crap in the yard and going around and under is not my idea of fun. I don't mind the extra pipe expense as I have plenty of SCH40 pipe on hand which I got for little money.
Based on your recommendations I am going to review the plan again and try to work it with laterals. If that gets to be a mess, I will have to do a perimeter run as that area is unobstructed and can access each watering area.
Thanks again for your reply, it is much appreciated.