Any of the short .277s with the 170s are gunna be mighty close ballistically to the .284. The 170s out of those are also going to necessitate a medium or long action which kinda defeats the point of going short and fat. If you are gunna have to build on a long action why not use a .280 rem or .284 win to get ballistics that are pretty close to the same as the .277s in a package that will feed smoothly without any extra work and probly hold an extra round compared to the ss or wsm? You can design that gun to preform best with lighter bullets than your existing .284 or find a reduced load that uses components you already have for simplicity. Now that that's out of the way. The wsm or ss on a short action 700 with 150 and lighter bullets will keep you in a lighter recoiling cartridge. With a wyatts extended mag box you will have plenty of room to seat vld or or copper bullets out far enough not to crowd powder space too badly. Hammer hunters or tsx's should provide plenty of penetration for occasional pig shooting. I cant promise but I would bet that the wsm 2 reamer from ptg has a long enough throat to let you load long bullets further out of the case without making them too long for the 700 short action. A build like that would take better advantage of the short cartridge and help diversify the ballistics of your collection a bit more.