FBReader for the iLiad can read DRM-free MOBI files (and many other DRM-free formats), and it can use any font installed on the device. For a couple of screenshots see
Mobipocket Font Switcher #22. Note that your web browser may display a degraded version of the images - if so click again to see them full size. I use
FBReader 0.8.4, because the 0.8.14 version does not allow access to menus (e.g. to switch fonts).
As you can tell from the name of the thread referenced above, it is possible to switch the MobiPocket Reader's fonts, but the default choices are limited, see
Mobipocket Font Switcher #19. All is not lost, though, because it is possible to completely replace the iLiads default font and therefore get a new MobiPocket Reader font, see
Mobipocket default font?.