I find that changing data design via ACCE is slow process and might cause human errors. Propagating changes from one environment to another seems to be quite tedious as well (for example from DEV to TEST).
Is there way to easily propagate data design changes to other P8 environments? Maybe it's possible to write some kind of update scripts?
FileNet actually ships with a program called "FileNet Deployment Manager" FDM.
This helps take the tediousness away from pushing changes from dev through to prod.
If your prod environment is already established, you would most likely need to rebuild your dev environments from first deploying from production backwards.
I would suggest looking into this tool, learning its strengths and weaknesses. It has helped us out a bunch.
BTW FDM has vastly improved from 4.5.1 to 5.2.1. You can deploy global objects like Marking Sets etc.