Hasbro, heres how you do it...
 

Ok this ones for all the bad ass customizers, and folks here who take it to the next level! I want us to collectively put together a running list of every character Hasbro could easily make using existing molds (for the most part, maybe a new head, or specific unique part) try to keep it easy kit bash and paint. I'm a 3.75" guy, but you ML folks feel free to chime in too...

1. green Quicksilver: regular QS, painted green
2. white Vision: new DD buck, Vision head, painted white
3. Shaman: Cyclopes buck, Thunderbird head, paint
4. 90's Cable: Hercules body, Cable head, pads, straps.
5. Tigra: straight Phoenix repaint, tail.
6. Kree soldier:new punisher buck, new head sculpt.
7. Vulture:spider man buck, falcon wings, new head.
8. Agent venom: FF spidey, pads,gun holding tentacles.
9. Exodus: Cyclopes buck Warpath head, Hyperion cape, new back blade things, paint
10. gold Ultron: ultron...painted gold... duh.

I know most of you guys are better at this than me.

ML Selene: Would a repainted Viper head work with the newer Emma Frost? I know the outfit that she'd be better suited to is the first ML Emma but I'm thinking that head is too big for that body. And quite honestly that sets you up very nicely to create Morgan Le Fey and Sersi as well perhaps just different bodies for those.

And OMG Exodus! Do It Hasbro! Great custom recipe.

ML Polaris: Scarlet Witch body repainted with Rogue head. This would also work well with the smaller scale.

I am thinking in both scales that somehow Dr. Strange's head would work well for both Graviton and Count Nefaria but need some help on some ideas for the body.

ML Grim Reaper - Bullseye body repaint straight up with the helmet "horns" reshaped, new scythe hand.

1. LOVE a White Vision....(keep the silver age one a holy grail piece)
2. AND AGENT COULSON!!!!!!!!!!Professor X body and new head
3. Moondragon female buck,Gladiator cape,bald head...done
4. PLEASE PLEASE PLEASE give us a Tigra!
5. EXECUTIONER as you promised...
6. Madame Hydra... female buck, Pyslocke head
7. Annihilus.... I dont know, just make it happen!
8. Re-release troop builders under the MI flag
9. Agent Coulson
10. Galactus Heralds box set

Nova(the galactus herald): human torch variant figure without the 4 logo and a plastic q-tip with flame effects on it.

Here's my ideas (coming at ya K dub !!!)
Spy Master (union jack head, punisher body paint)
Grey Gargoyle ( Kraven redo boots add cape jacket thing paint grey)
Bartroc (K dub has shown us that one !!! )
Titiana ( straight She- Hulk repaint and add stubbies ifya want)
Shroud ( Cloack change head and a lil paint theres one on ebay)
Chemestro ( first one...Thunderball repaint )
Chemestro II ( Old cyclops Spiderman head paint)
Graviton ( leader/ skrull body Dr strange head slight molding)
Viper ( Pyslocke head or Sue storm repainted Avengers Black Widow body)
Powerman( Masters of Evil Version..Legends Giantman repaint)
Oh and for your Kree Kabosh....we could use a Red Guardian head already has th fin on top ;-)

01 Tomb of Dracula using Professor X body, Namor head, Vision cape
02 Jigsaw using Professor X body with new head
03 Void using entire Sentry body
04 Shroud using Steve Rogers body, Moon Knight cape, new head
05 Danny Ketch Ghost Rider using Ghost Rider body, new torso
06 Kree - using Red Guardian entire body, head
07 Titania using She-Hulk entire body, head
08 Speedball using Steve Rogers body, new head
09 Namorita using Scarlet Witch body, new head
19 Shang Chi using Iron Fist body, new head

Captain Marvel: just use the female buck and give her a new head THAT'S ALL YOU NEED TO DO COME ON

a couple more...
1.Sting Ray: Cyclopes buck, Spiderman head, new cape, paint.
2.Cannonball: Ghost Rider buck, Angel head, Goggles, paint.
3.Living Laser: skrull buck, new head, paint.
4.Ka-Zar: Kraven buck, Warpath head, paint
5.Attuma: Hercules buck, absorbing man head, new helmet,
6.Dr. Druid: FF Spidey buck, new head, Cloak's cape.
7.Machine man: Multiple man repaint, goggle retooling on eyes.
8.Moonstone: Ms.Marvel repaint
9.Squirrel Girl: Wasp repaint, Rubber "fur" arm, leg, and body pieces, New Tail.
10: Venom!: (yeah can you believe we have not technically got him yet!) Hercules buck, new head hands and feet.

I really like this thread. Gives me some ideas I hadn't thought of....but sadly makes my needs increase drastically...Anybody have 3 extra Red Guardians?

Also I have made a handful of the ones listed by others a lot easier than you may realize here are my ammended ideas from others above:

1.Vulture- Falcon Buck and wings and an Iceman head (Once you paint it flesh toned you would never guess it was Iceman)
2.Ka-Zar- Namor buck and Age of Thunder Thor head (I also used the "tunic" from thor I just painted it brown)(This is one of the easiest customs and is unmistakingly Ka-Zar, I did use Kraven Necklace too)

I know we are trying to encourage Hasbro, but these can be done with other toylines not made by them.

1.Shaman- Any buck with Boots (I used Hawkeye with different arms)and the head from Nightwolf (Mortal Kombat Line)
2.Annihilus- Ultron head and the Redakai figure Warnet (wings could be better, but it works)

Also I will probably take the advice above and make Madame Hydra and Jigsaw really soon.

Kylactus I'm still working on my Lady Deathstrike, Thanks again for Electra and Jean.

can't wait to see it man! I love your work!^^

Heres a super eaaaassssy one :
Madame Masque = Mystique body (dont even have to paint cause the blue looks like a outfit) and a Pyslocke head apply gold mask