A major issue with putting non-incidents in the Incident table is the precedence. For the Incidents that are projects, you need some way to identify them as such (usually a category field of some sort). Then you'll start getting Request infiltration into Incident. You may already be feeling this with Problem as well. Sooner or later you ask yourself why users hate using a massive confusing incident form, and why you spend so much money on a tool that doesn't tell a good story of the work.
In my experience, by using the provided modules as intended you can tell extremely powerful utilization stories by simply showing a group of tasks by their task type.
Guess what my group spends most of its time doing. Tasks from fixed workflow. But 33% of the work is Incidents, which means whatever my group works on experiences massive failures.
... or does it? If I'm tracking all kinds of other stuff in Incident (training requests perhaps?) it dilutes all reporting.
