How to Keep Content Types Current with Updated Data

Question

Let’s say that I have four content types—content type 1, content type 2, content type 3, and content type 4—all based on the same list, say list A.
Each content type has its own workflow.
When the workflow for content type 1 is completed, the data is saved to an individual item, say item Z, in a separate list, list B.
When the workflow for content type 2 is completed, the data is saved to the same item (item Z) in list B. The reason that there are two lists is that the creation of content types causes new items to be created, but the each
new item must reference data from the previous item. That means that data has to be copied from the first item to the second item. But what happens to the data in the second item when data from the first item is changed? The solution is to have a single item
in another list to which all content types write their data.
What I need to know is how can all the content types retrieve data from list B when those content types are based on list A? For example, let's say that content type 3 uses data originally input through content type 1. As the
user inputs and saves data through content type 3 he sees data that had been originally input through content type 1. Another user then accesses content type 1 to update and save data through it. When content type 3 is opened again that user will not see the
updated data entered through content type 1 because it is tied to a different item. The solution seems to be for all content types to save their data to the same item in another list. But then how can those content types be designed so that when they open
they show updated data from List B when those content types are based on List A?
Other applications have the notion of a folder containing all the up-to-date data fields. Another way to look at this problem is to state what SharePoint 2007 does to mimic the notion of a folder.

Answer 1

Thanks for responding, but I don't think that the solution provided solves my problem. What you described will keep the item in List B in sync with the changes made to List A. However, the content types from List A will not be in sync when they are opened
from List A. Say content type 1 makes changes to various fields. When content type 3 opens it displays some of the fields that content type 1 changed; however, content type 3 and content type 1 by definition display different items--and those items are not
in sync. Either I have to copy the updated item from List B back to the related items in List A or there has to be another solution.
Is it possible to have a workflow update all the items in a list based on a key field whenever changes are made to that item. Say content types 1, 2, 3, and 4 already exist and each refers to a different item in List A, but they are "tied" together
by a key field. When content type 1 is reopened and changes are made, is it possible to iterate over the items in a list to find other items whose key field matches the key field from content type 1? If so, then when matching items are found the fields in
them can be updated by the same changes made to content type 1.
If this latter scenario is possible, how is that iteration set up in a SharePoint 2007 workflow? Thanks again.