Mutated Horses = Great Idea
Mutated Horse Armour = Not that great
But seriously, everything stated in the OP is exactly what needs to happen, but first they really do have to choose an interesting location, because fuck me was the Mojave Wasteland boring.
Just have Bethesda work WITH Obsidian, that way you get the best of both worlds, and increased manpower means less bugs, less workload, better writing, better idea implementation.
I am one of the few who preferred FO3 to New Vegas, probably because that's how I discovered the series, but there was just more of an atmosphere altogether.
They need to use Hardcore as Default, and then turn it off at easier modes. They need better, more customisable houses. It needs some kind of faster transportation, horses would be great, they could have 8 legs like Sleipner
Although that might be a ***** to animate.