Can I leverage a dependent enumeration to filter values from a contributor list?

It sounds like you want something similar to a role-based enumeration (where you can say what value to default to based on the logged in user's role). For example, if the logged in user is a Product Owner, then the default value for Priority would be set to High.

But you actually want to take that a step further (if I understand) so that you can set the values in the dependent list based on the name/id of the individual contributor. So if your list of issue managers contains Bob, Ted and Alice, if someone chooses "Bob" in the person list, the list of Regions (for example), would only include areas in the south east (Bob's region) and if they chose Alice, the list of Regions would only include areas in the north west.

Since the list of Issue Managers can change (as people move, leave, get promoted), the configuration would not be quite as clean as a normal dependent enumeration since the driving list could be very dynamic (unlike the typical Operating System -> Browser example).

If you were using RTC 4.x (or if that's possible), I'd suggest looking at this article: https://jazz.net/wiki/bin/view/Main/AttributeCustomization#Dependent_Enumerations_4_0 that talks about improvements in support for Value Providers that seems to match pretty closely what you want.

If moving up to 4.x isn't possible at this time, you might consider using a Custom Filtered Value Set Provider as discussed here: https://jazz.net/wiki/bin/view/Main/DataSourceValueSetProviders There may also be an interesting way to use an HTTP Filtered Value Set Provider -- delivering the values this way may make it easier to maintain the relationships since the persons doing that would not need to have permissions to make process specification updates.