I want to be able to create a custom field that is used for 2 different issue types – say Bug & Improvement. For Bug issues, I want the options to be A,B,C,D. For Improvement, I want the options to be A,B,D,E,F.

JIRA only allows me to define 1 global context – not having to select specific projects – for the custom field. So if I set up a context for Bug issues w/ options A/B/C/D regardless of project, if I want to then define the context for Improvement issues with its separate options, I'm forced to explicitly select one or more projects to apply this to – even though I want it to apply to Improvement issues in all projects.

This is a serious maintenance problem. As soon as I add more projects, I now have to remember to go back to my custom field and add those projects to the Improvement issue context. That's ridiculous.

Is there a workaround for this?

If you made Project Categories a 1st class, usable object in JIRA, at the very least you could allow us to define a separate context by Project category which would then automatically apply to all future Projects in that Category without having to explicitly add each & every Project into the Custom Field context as new ones are created.