Jarvis, are you talking about using it only for estimating? Or, if we assume that schedules are to be considered as predictions of time, effort and cost (at least until actuals are entered based upon what already occurred), then you are already using it as an estimating tool. If, however, you are referring to at least a semi-automated way of incorporating the basis of the estimates data, we would need to consider the following:
Do you have historical data that is appropriate for re-use? For example, incorporating repeatable processes as work packages within your project;
Are you referring to software development or engineering-design-development estimates? If so, do you already have a preferred estimating methodology, such as a parametric or an analogy model?
Have a look at an application called BOEMax, which is a separate app that exports its data into MS Project, maybe that would fit your requirement. I haven’t used it, but I have heard that there is heavy use of the package in fed contracting, and it appears to allow for some pretty detailed recording of bases of estimates at the work package level and is independant of estimating methodology. I think the company who created the application is called Projstream.