What happens to closed / completed opportunities in a typical workflow

I work for an Architectural practice and having looked at a few different CRM options, Suite CRM would seem to meet our needs.

I’ve had a fair bit of experience with Open Source projects (Drupal and Wordpress mostly) and Open Source CRM systems for a different purpose (CiviCRM), so am relatively comfortable with the idea of customising / tweaking things to suit the way we work

One part that I’m a bit confused at (with most CRMs, not just Suite CRM) is what should typically happen to Opportunities once the quote is agreed to and the contract is signed. From what I understand of the default method, is that there are various steps through the sales process and then you pretty much jump straight to completed won. After that, anything else that follows on is a support query or similar (bugs etc).
from our point of view, this is not how this works though - we go through a load of steps to get a contract signed, similar to the default process. The Opportunity if it reaches this stage then becomes a live project, which typically goes through a number of stages - concept design, planning drawings, building regulations drawings, tender drawings, tender, construction etc. After that it becomes a completed project at which point the support options (logging defects and responding to ongoing queries) might make sense.
At present, the option I’m looking at (purely as a diagram on paper at this stage is creating a new module for the Live projects, based on the Opportunities (Much of the data is similar), but with a category for the work stages. Once we receive instructions to proceed on a project, we would then convert the Opportunity to a Live Project.
A similar process would occur at the end once the project was completed and it falls into an After Care category of some sort.

My question is, does this sound a sensible approach to take, or am I misunderstanding the way the system is meant to be used?

At the end of the day, we’d like to be able to use the system to easily review the status not just of Leads / Opportunities, but also of Live / Completed Projects, so that reports could be created that could for instance give the status of every project in the office at any one time (say 40 enquiries in progress and 10 live projects plus dead and completed for that year) or a list of locations of all Opportunities / Projects / Completed projects (ideally we want to then display this on a map - currently we use Google Docs and Google Fusion Tables to achieve this).

Any thoughts / suggestions would be welcomed.