Perhaps if WW crew were prepared to do the long range flights under the same arrangements as MF, they would keep them.
So SAN, GIG, PHX, all one night away and only one/two days MBT. You still want to keep them.... no I didn't think so...
You now have competition within BA, if you can't match it then you will become extinct. Same as in any form of business.
And WW keep all the money from routes they lose anyway, so why does it matter?