If you want them to shed their fleece then you need two generations to get that trait back.
I keep Wilts and the feller that sold me them is working on his own 'easy care' Wilts x Lleyn which sounds promising.
So you would have to cross your BWM to a Wilts ram and then the resulting progeny to another (Unrelated) Wilts ram. These would then have the shedding fleece. I imagine they would be somewhat smaller than a Wilts, you could then use a more prolific terminal sire, perhaps a Charollais.
The 'easycare' traits of Wilts are as follows: Shedding fleece, so no shearing and flystrike is rare (base of the horns is an often overlooked site for flies), Will lamb outdoors in most weathers, good feet, thrifty - will finish on grass, shouldn't need feeding when stocked sensibly (I work on 3/ac, and the landowner takes a hay crop off a third).
The down sides to Wilts are: Not very prolific (lamb at about 135%), incapable of rearing triplets (if you ever see them), Very rarely accept a foster lamb (which isn't that much of an issue with a breed where triplets are rare), difficult to confine and a bit of a git to handle (I don't mind this, but I am a 6 foot feller).
Most outcrossings are an attempt to increase lambing percentages and to make them a bit more placid.
I like em, but thats just me, I like terriers too.