Working on a 1/2 fat right now and debating doing something with the rear as well

I'm working with a 29er and I have my front wheel in hand, a 2.7 Nevegal mounted to the marge lite wheel does fit but I really wonder if it's worth the effort and $$$, might also have to go single speed or geared hub etc

The geometry would be slightly off (about 3/4" lower in the rear)

Maybe I should go with a Krampus rabbit hole rear with just a wide 29er tire so I can drop the pressure more? I can run most 2.5" tires with no issues (on 24mm wide rim) it wouldn't require any drivetrain modifications etc

Is there any real advantage to going with a wider wheel in back?

I assume it's not going to ride deep sand as well as a true fat bike, am I wrong?