The best of the works for when "things start to unravel" or as you put it "plans start falling apart" is undoubtedly the 358 NM. Forget all the blather about bullet selection as all your mentioned cartridges have adequate bullet selection, for your needs. I have hunted with all your mentioned cartridges except the 358, but Why not? and I have a very good friend who used nothing but for many years and many head of game and it is a killing machine. Animal presentation doesn't matter to the 358 NM when using 250 gn Parts or some of the newer premium bullets. Of the cartridges you listed, I am the least impressed with the 338 WM and have seen several failures with this cartridge. Another good hunting buddy used his Whelen for many seasons and never found it lacking with 250 gn Speers on anything including big bears. Myself and Why not? have used the 9.3 on game and neither of us has found it lacking either, Ted has used it much more than I.
In my opinion though, you have overlooked the finest cartridge of this class...the 340 Wby....as you stated you reload so ammo cost is not a concern to you and you can grab 100 R-P 375 H&H cases and run them through your die and voila, you have 340 Wby cases for the price of 338 WM. I won't dwell on this because you did not include it, but If you are considering the 358 NM you really should consider a 340.
As far as magazine capacity goes there are a number of rifles that hold 4 and 5 magnum cartridges under, my Sako Safari holds 5 mags under as does the CZ and the old Brno 602 and the older Sako L61R-A IV all hold 4 mags under. Plus there are several makers of larger capacity bottom metal, for a couple hundred bucks.
The 35 Whelen and 9.3X62 really shine if you want a 20-21" carbine style rifle as their high expansion ratio makes them very efficient in shorter barrels, however you asked for comparisons in a 24" barrel, where the 358 NM has no peers with the group of cartridges you chose. The 358 is a true step up from the rest and is just a slight notch below the 340 Wby or 375 H&H, but make no mistake nothing is free and the recoil is on par with the 340/375 and is a significant step up from the rest as well.
There is another candidate that you overlooked in this group, that I have taken many head of game with, and that is the 350 RM.........this little guy hits 3 classes up from where one might think it belongs and kills all out of proportion to it's diminutive appearance. Although not significantly better than the Whelen, it is slightly better and works through a short action and is also conducive to shorter barrels. I used to scoff at my buddy who used this cartridge for everything until I bought one and hunted with it, let me tell you it made a believer out of me.
There are so many great cartridges in this category that selection can only be made by personal preference, and very few would be wrong for your stated purpose. If as you say the sh!t is about to hit the fan I would be quite happy standing there with the 358 NM, the 9.3X62 or the 35 Whelen.........in that order, of the cartridges you selected.