I am looking to overlay mappoint with a geocoded .tiff overlay showing RF coverage for a state while still maintaining the ability to zoom to the street level. Is this even possible and if so...how do I accomplish this?

Hi,

One thing that comes in mind is to put a transparant panel on the control aligned with it. The panel will intercept keyboard and mouse. On this panel you can put a transparant bitmap.

For pan and zoom you need to do some calculations to find the xy points in view and to pan / zoom the bitmap. A little tricky I think but should be possible.

Maybe someone else has better / other ideas ?

If there is only one possible place to zoom in and out, you'd still need a tiff for each zoom level. It won't work if you go any further than this.
An alternative may be to capture the required area of MapPoint into a PDF
with your overlay as another PDF open beside it. I might be able to help.