A Jira 'Priority' is really 'Severity' - could we specify a Severity and a Priority instead?

We've been using Jira for a while and generally find it the Mutt's nuts. One thing which has never quite seemed right though is the assignment of priorities to Tasks, Improvements and New Features. We think it's because the priorities in Jira are really severities of bugs and not priorities at all. It would be great to be able to assign priorities to issues that really do relate to the amount of time that should be spent on them.

For example, if there is some corner case whereby a very specific set of actions can cause the system crash, the severity of the bug is indeed 'Blocker'. However, it may be that no-one in their right mind would ever do such an odd thing and that it is more important to the clients that we fix more pressing things, which may be 'Minor' or even 'Trivial' severity such as a typo on the main page.

In the same vein, none of the available priorities really seem appropriate to requests for improvements such as this one.

So my suggestion is to have a set of Priorities from 'Urgent' to 'Yeah, whenever' and maybe assign the existing 'Severities' to bugs only. How on Earth to retro-fit that into existing databases would then no doubt be cause for discussion!

What do you reckon?

Mike