You seem to be getting a lot of graphics from pc mario engine games. I also saw your list of suggestions on hacking ideas.
The castlevania sotn 16 bit hack could probably work using something like super metroid as a base. That community is great at manipulating the physics in that engine so I assume it could actually be done. Some color compromises would have to be made but, as you've said, shown, and done, it's possible. Some of the bosses might need to be downscaled but who knows when shit like this is possible:http://youtu.be/Xx-oNUud0Qk?t=7m5
EDIT: for some reason, this link is borked. Go to 7:50 for my example.
I'm more interested in your suggestion of using metal slug assets from mario fusion. Do you really think there's enough room for all the exgfx that would be required to do that in Super Mario World? I honestly don't (shit, I couldn't even get Mario's Wacky Worlds foreground graphics to fit) but there was one level in the unfinished ASMT2 that kinda proves me wrong, seen here:http://youtu.be/1ViJxBRF3O0?t=6m10s
The other two (Wario Land 4 and Super Mario Country) seem easy to do, with compromises of course but yeah, they could be done. For proper Wario graphics, you will either have to do one of two (maybe three) things though.
Option A (aka, easy option): Use powertool. You can make the character about doubly as big and use independent exgfx for player graphics, but there's a downside. It glitches out the yoshi berries (not the biggest of deals to make new ones though in lunar magic using exanimation) and the upwards walking animation on map. They both still work but they look wrong and, even If you replace the berries, the visual glitch on the map is so annoying that when I use powertool in my hacks, I tend to lean towards not even using an overworld. That may just be an example of how bad my OCD is moreso than how bad the glitch is though.
Option B (HARDEST option): Create custom asm code for how the player graphics are read. I'm not capable of this nor can I give you any helpful suggestions past knowing that that's possible. I know, I suck.
Option C (the big maybe): Wait for dyzen to be finished. It's new and it seems amazing. The patch uses a new method for dynamic sprites which sounds bad (all those dynamic sprites made already are useless with this) but it's more than that. Not only will dyzen allow you to convert those sprites manually, but it will also let you create your own dynamic sprites (or NON-dynamic. That's right. The SMW hacking community may finally get that long sought after sprite creator tool). How does this help you with making a playable Wario? Well, from the creator's last post concerning what will be released in two months (not sure why two months specifically. Is another c3 around the corner, ha?), it may replace power tool also:
"- Support for your own player (only the graphic routine)."
Unless I'm taking that out of context? I hope I'm not though, because as is, power tool is amazing for being able to add new types of Mario gameplay, but it's simply incomplete. Like 85% done and, as far as I can tell, Bio, the creator, said he was going to fix those things but has gone under radio silence on it since then. It's a shame. So far, I've made custom Cat Suit Mario suit, Bunny Suit Mario and a new Frog Suit as well. They all work amazingly well in gameplay but yeah, to get that capability, power tool asks you to scarifice too much, in my opinion.
Anyways, good luck on this, sir! I hope you eventually realize all of your mario world dreams. If you need busy work help ripping graphics, hit me up. I'm actually really good at that, ha.