Customizing the Issues List: This is fine, as long as you do not delete any of the default columns (especially Status and Category). However, the catch is that, any new columns you add are not available in Reporting Database for reporting, and will need some programming to retrieve from the Content Database.
If you stick with default columns ( you can have the values of those columns deifferent), these are available in Reporting Database to report on, and there is a readily available report under Sample reports to look at Issues and Risks.
