Without the restriction of "can be done", I'd like to see the following:
1) IDW G.I. Joe FSS (Krake, Monk, Urzo, Tripwire, Mainframe, Light Horse, Hot Sauce, Copperback, Ronin, Chameleon, Firewall, Headman)
2) Cobra Stinger (POC VAMP Style)
3) Updated APC (fit 4" figures)
4) HeartWencher and 4x4 truck
5) "Proving Grounds" Con set - Battle Force 2.0 vs Cobra Drivers (WORMS, Moto-Vipers, Ferrets & Nullifier)
6) SEAL 3-Pack (Torpedo, Wet-Suit, and Deep Six in non-diving suits)
7) Cobra La Royal Guard 3-Pack
8) Famous Joes 3-Pack (Fridge, Sgt. Slaughter, Rocky)
9) Pick your own 3-Pack (any 3 Club produced figures since 2011, pre-order only)
10) Un-produced FSS (Un-produced figures from Hasbro Vault - Renegades figures, Ver2 Rock-n-Roll, Snow Serpent, etc.)