There is actually a way that the vacuum disconnect would be great.

If you spool the front end, then use the cable actuated disconnect (instead of the vacuum unit), then you could run it in 3 wheel drive (which works great actually!) and then just pop the disconnect to lock up the other front tire when needed. Much like an ARB, but you'll always have the left front tire moving when in 4x4, and will have the option to lock up the fourth at will.

If I run across a killer deal on a vaccy, then I'll use it. Spools are cheap as well. A lot cheaper than a locker in the front.