Hi Corky.
We do not have any row security on the UDC table. I, too, have heard multiple times from JDE/PS/Oracle that UDC row security was strongly discouraged.
No one outside of our central support team has access to edit the UDCs themselves (P0004A). For most users it is secured out. In key areas like business units, branch plants and the chart of accounts we use column security to prevent changes to the assigned UDC value (P0005S). Only a handful of screens are involved. Each location has one or two users who can selected new values. In our case the UDCs on business units change frequently. The field can plan for new values and submit them in advance to be added the system. We allow selected users, typically the local support team or key super users, access to these columns for update.
If your users need to add 100 to 200 new UDC values daily I would still restrict it to two or three people. That volume is not so great that it could not be funneled to one or two users. And if they are adding that many there must be a convention used to create them. It may even be possible to preload a lot of values based on your naming conventions, reducing the daily maintenance. Some user process changes could be required also. But the UDCs are too sensitive an area to leave at risk.