Man, I used to know all this stuff like the back of my hand.... Ha! just want to make sure I got this lined out before I hand a pile of parts over to the mechanic. It's good to be back looking at Zuki stuff, even if my bank account doesn't agree....
I run an Anvil with an ARB locker. You are correct, yank out the old diff, install new locker and reinstall the new bits. My only concern would be running a non switchable locker on the front but I know lots of guys do it successfully.
I do agree with skitime, But your bank account will really be screaming if an ARB is thrown in the mix.
Last weekend I came off a really steep climb onto a curve on blacktop. While my ARB's were engaged it was impossible to turn. Flip a couple switches and run straight for a few feet and easy to turn again.
IMO do not put another locker or spool in back also, a limited slip would be ok (because it should slip when turning). With both ends locked on a hard grippable surface and it will just want to push straight ahead.
With your hubs disengaged (for road travel) there would not be an issue as both are free from drive train.
Ifthe locker was in back you would have to put up with the issues of how the locker works all the time.