Honestly it would remove the whole point of raiding for many people, raiding is meant to be like end game for this game which is something it is sorely lacking. Wasting time and resources into a 5 man raid (which I've never seen anyone ask for) is a terrible idea and those resources should be moved onto something else. Maybe instead have the current raids scale so that it does not matter how many people you group up with.
Put those resources into the Thanos raid and Red Axis, or other new type of content.