4) In contrast with the drawbacks/demerits/flaws of A, B can serve as a better step/move/advance in the right direction/to ward the solution for the problem of...
与A的缺点/缺点/缺点相比,B可以作为更好的一步/朝着正确的方向/朝着解决……
(e.g. In contrast with the drawbacks caused by nuclear power, the solar power can serve as a better move toward the solution of the problem of energy crisis.)
5) So when it comes to an effective remedy for/a good counter-balance to the problems/limits/faults/weaknesses in A, people naturally think of B.