There is a flail & light blade combo called Kusari-gama from Dragon 404. It is a superior double melee weapon. It's a sickle (or kama) on one end of a chain and a heavy weight on the other, with the weight swung with great force and used to either entangle or trip a foe, and the kama used to slice at a vital part of the body. It's +2 proficiency and does 1d10/1d6 damage with the Defensive and Reach properties.
That is the closest thing to what you suggest.
So, how exploitable would a heavy blade and flail be? Well, at what level? If you are talking heroic tier, then not very. If you are talking epic level, then I'd have to do some digging.
Thank you Ceika for the wonderful Avatar avatar!
If you are imagining heavy blades on a chain, as a weapon it wouldn't work. If you use it as a flail weapon it won't cut, it will bounce. Blades need pressure to do damage, and flail weapons simply don't provide the pressure you need. A whip can cut because its light and moves a supersonic speeds to do damage. If you spin up a blade on a chain and smack something with it, it might make a little nick but would most likely just clatter harmlessly off of any armor. The Kusari-gama works because it is a Light Blade in one hand attached to a chain in the other. The heavy weight (Hammer/Mace) works because it does damage by transferring the energy caused by the swing, that momentum actually amplified by the longer arc it can make.
So, cheese, eh, maybe. Actually work, no. Sorry Kratos, but without magic fixing physics, you aren't doing anything.
Kusari-gama is a double weapon, the mainhand end is a flail with defensive, and the offhand part is a light blade with the offhand property. The compendium handles double weapons very poorly in my opinion. And yes it counts as a light blade and flail at all times. It can take either enchant (for both ends, because double weapons use a single enchant), feats/powers that apply to either apply to both ends as well.