Yep, it would be perfectly possible, I am working at the moment(among other things) on a terrain engine that generates it's own heightfields with perlin noise... and loads them from file, although at the moment it likes power of 2 sized heightmaps... It still has some problems and is being worked on, but the actual terrain generation is all in place, the issues involve calculating normals smoothly across the map(which is multiple objects, soyou cant see the "seams" between objects.. mostly solved), and having the terrain deform properly while its non-square(possible to make rectangular terrain patches)
The only thing I would think about that particular bump map, would be that each pixel will end up representing a height(or being interpolated between a couple of verts). Because of that, you may find that you would need to scale down the height of the finished terrain to not have all the landmasses look like they are miles above the sea level, or maybe alter the contrast or something to make it not to stark..
Of course, the scale is something that you would need to consider aswell, It would be very time consuming and system intensive to generate anything close to scale of the earth. You would need to have fairly robust culling and lod in place to even be able to run something that large I think, but, if you are really wanting to I suggest searching through the DBPro forums for a user named "Visigoth's" posts regarding his "USGS Terrain System" .. Its quite easy to port over to C++ if you want to, and is capable of making very large terrains that look pretty nice.
If it ain't broke.... DONT FIX IT !!!