Rookhawk,
I'd just bring the .404 and no other, then merrily hunt all the species you mention with it.
Never having shot a leopard or elephant either one, please do take my following comments with a grain of salt.
Anyway, it seems to me that, since elephant are commonly taken at extremely close range, such an adventure would be a quite a bit more pleasant without the scope.
With that, could it be workable to sight your scopeless rifle in at 15 or 20 paces, with your 450 grain Woodleigh "solids" ? (or my preference would be a 400 grain meplat shaped, aka "coffee thermos" shaped monolithic true solid, at around 2150 fps).
After that then, snap your scope into the claw mounts and zero it with 400 grain Woodleigh round nose softs, for your leopard and "plains game" hunting.
Likewise, it seems very likely that, if you used all 400 grainers, your softs and solids can be made to strike to the same point of impact, with perhaps a little bit of reloading bench and rifle range time.
If you are not recoil shy like I am, you could adjust your velocity upward accordingly, since the .404 Jeffery is very capable of at least 2350 fps, with 400 grain bullets, all the while staying within safe chamber pressures (not that 2150 fps is not perfectly adequate already, even for elephant).
A Woodleigh soft is likely not a good thing to mix up during an elephant stalk and one would not want a solid for leopard but nonetheless, personally I prefer all of my ammunition for whatever rifle I am carrying to be "zeroed-in", all to the same point of impact.
Not having shot or even watched a leopard being shot (except on television), perhaps I'm wrong but, I suspect a .423 diameter "Woodleigh Weldcore" round nose soft will knock the spots off of any leopard, whether the bullet expands much or not.
Such is one of the reasons I generally prefer round nose and flat nose bullets, unless I am expecting shots to be past approximately 300 yards / meters.
At any rate, I look forward to reading the full report when you settle on what to bring and how it all works out.
Cheers,
Velo The Rifleheaded.