I’ve never built a house, and I’ve certainly never dealt with one of these “plan” houses. So I don’t know what you get when you buy. Just the plans and details? Or is there some kind of kit that gets delivered over time?
Assuming you don’t get pallets of parts, you’ll still need a general contractor. You can do that yourself, but it takes more thought and time than most people realize to coordinate (and cajole) various independent skill contractors. (That is, you’ll be subcontracting certain work, as you have specified, and you’ll need to be sure that the appropriate work is done on time so that it doesn’t impede follow-on contractors.)
I’m presuming that you’ll subcontract all of the civil work, for example: the digging for the foundation / cellar, pouring of the foundation or basement, drainage and water supply piping and so forth. You’ll need to bring in temporary power to the site from a drop at the street, and that will be another subcontract after the civil work is done or well underway (and there won’t be any interference). In town, you’ll need to manage and coordinate tie-ins to the sewer and water lines, or in the outer suburbs you’ll need more civil work: a well and a septic system. You’ll need to order and pay for materials as you go, and you’ll need to manage their storage and proper disbursement to the proper aspects of construction… or you’ll have to re-order.
You won’t want to order all of your materials at once, because storage, pilferage and vandalism are real headaches, and your site would look like Home Depot after a tornado hit – and be about as expensive, too. So you have to carefully monitor all progress and be sure to order materials as needed, and coordinate with delivery people to be available when they will drop the load, and where you want it.
When you start to line out an actual plan of “what” and “when” and “how long to complete” you’ll start to realize the real value of a contractor working a time-based plan (where he doesn’t get his money until the work is done). Incentives work!
If you can live with the fact that twenty years on your siding still won’t be complete, most of the interior trim still won’t be put up or stained, and the yard still has construction materials lying in wait… then it might not be so bad. I wouldn’t build my first house this way, and I wouldn’t build a dream house this way… unless you like nightmares.