A subsonic centrefire set up would get the best out of an integrally suppressed rifle if the barrel is short, ported and the moderator is removable for cleaning. The load would need to be developed to bring the velocity just below the speed of sound in e.g. a .30cal. Coupled with a laser range finder ballistic drop scope it would be an interesting tool for the occasional, very specific purpose. In the mold of:
MP5SD - Heckler & Koch
However, as interesting as this would be the total length is rarely a critical issue for stalking or fox shooting etc and so the marginal benefits of integral suppression are likely to be outweighed by cost, weight and maintenance (and legality for minimum velocity etc).