My company has been using JIRA as a requirements tracking tool as well as a bug tracker, and it's been working pretty well while we've been working on one project at a time.
We now have a scenario where we have three different project proposals whose requirements partially overlap (e.g. requirement 1 applies to projects A and B, requirement 2 applies to projects B and C, etc.). I'd like to be able to enter a single JIRA issue for each requirement, but that doesn't appear to be possible since JIRA issues and projects have a one-to-one relationship.
Has anyone found a way to do this in JIRA, or maybe with some other tool that integrates with JIRA ?
While there's no single correct answer, I can offer an idea. I don't have enough information about your work process, but you mention that you have project proposals. So I'm assuming projects A, B and C are in early stages. Requirements gathering and such, no bugs yet.
Set up a single JIRA project, say, "Early Requirements". Put all the requirements for projects A, B and C into that JIRA project. To allow many-to-many relationship between requirements and real projects, set up a custom field of type "multiple checkboxes" or equivalent, and configure "project A", "project B" and "project C" as its values. For any requirement you can check which project it applies to.
Now - and I am making more assumptions here - let's say some proposals move on and some die away. You will need a process to a) extract all the requirements for real project A into a newly created JIRA project for A - this can be done via search & bulk clone issue; b) purge all requirements that have no live project associated with them - search & bulk delete.
Caveats: if you need to share requirements with different customers, it will get tricky. Permissions are configured per JIRA project & issue type.
Having said all that, JIRA lacks features for decent requirements management, such as baselines and traceability. But it may be ok for just collecting data for further work.