Starting a new project

After a long separation from Filemaker I'm back and I have a new project.  I am creating an inventory system for a high end retailer where they sell unique individual products.  I hope that you will be able to help me get the concept right from the beginning.

Generally there are about 10,000 stock items of these half will be non repeating items that we be reported on by a style of Item.

There will be about 5,000 items that will be repeated but in total there will be only about 10 shipments in for each and 20 to 30 units in total of them.

Finally there will be about 300 items that would have hundreds of purchases and sales.

There will be manufacturing where one piece will be made from others (I have made these systems in the past).

I will need to be able to report on stock levels today but also on a date in the past. While I have ideas how to manage this I'd like to get others ideas how best to tackle this issue.

I will need to keep seven years of information at least

I will need to allow for growth of the business

I presume that keeping quantities of and values of stock should be done on the Movements record.  In other words while my stock record will have a value for qty in stock this will be a calculation from Stock (purchases and sales and manufacturing) movement lines.

This record would have fields as follows;

MovementID.p

StockID.f

Date of Movement

Purchased Quantity

Purchased Value

Sales Qty

Sales Value

Qty After Movement

Stock Value after Movement

How would  would I calculate the value qty from a previous date?

Is my Schema of how I want to keep the data sound?

Are there any areas that I would particularly need to consider in this type of business?

Your comments are always very helpful