Re: 284 win build
You may have issues with feeding from a long action magazine with the .284 Win case. In theory it sounds do able, but I've seen Long action rifles that needed the bottom of the reciever opened up for the .284 Case, as it's a bit fatter than the .30-06 Family of cases. Not so sure with the detatchable case.
I'd personally consider a .280 Remingtonas well if you're looking at that class of a cartridge. The only diffrence between the two is the shorter powder column for the .284 Vs the longer for the .280 Rem, If I'm not mistaken the .280 Rem does have a slight case capacity advantage due to the shoulder placement, which is forward of the standard .30-06 Case.
If you are going with the .284 Win, Some gunsmiths are able to cut a longer throat for the longer bullets, however if this is done it severely limits you to the type of bullets and bullet weights used. Mostly the heavys...
If the chamber is cut standard, you still have the best of both worlds, a long action .284, seating the bullets all the way to the lands on most if not all loads. That speaks of good accurate setup. The feeding can be resolved by a good gunsmith, so this is certainly a viable option.
Just my thoughts,