I'd still advocate for a hard mode with buffed enemies and 6 party members, though! More tactics, appropriate opposition.
With buffed enemies you mean just more hp? I'm no programmer but that sounds relatively easy to do. Or not? I'm not a friend of a party of 6 because I see a lot of work been put into balancing which should go into a wider and deeper story, more locations, more quests, not "doing it with 4" and "doing it with 6" efforts. Balancing with the normal difficulty sliders, as often pointed at by the 6-fans, would not work on the hardest difficulty, so that's no option. But if the party of 6 could be achieved with just an hour of work changing hp, why not.
There can be no discussion, the goblin fights were a lot more difficult shortly after release when they had a lot more hp than they have now. After I lost my first fight against Gutt I even stopped playing for a long time because I had no clue (except barrel use or similar cheesy crap) how to go throught the fights with normal use of the chars. A party of 6 could have been a remedy. But who knows (except Larian) wether it is soo easy?