In some respects, these are pretty neat, but in others I prefer the actual sets. For instance, XPlode's torso feels lumpy and not very cohesive. It doesn't help that his waist in your revamp is practically the widest part of his body. Also, his back feels hollow and not very substantial. So in most respects I prefer Cirkit's revamp
to this one.
Corroder is probably the nicest-looking of the bunch. While I really liked the original set's design, this design comes really close in proportions and aesthetics.
Meltdown is also nice, but his hands/tools could use improvement. Specifically, it feels weird with his tools standing so far off his wrists. I think he would be better if his "claws" were attached directly to the "shield" pieces on his arms, as was the case in the original set.
Thunder's an interesting case, because while he doesn't look entirely cohesive, the same could be said of the original set to some extent. You did an absolutely magnificent job with his tools, IMO. But the tubing pieces on his torso feel somewhat out-of-place, as does the bulky shoulder armor he has. Although it might limit posability, I would think a 2.0 torso shell in Silver Metallic, attached like the shoulder armor of Jetbug, Stormer 3.0, etc, would better emulate the shoulder armor he has in the set. Your shoulder armor design is nice (I can see you borrowed it from the new Bulk), but I don't think it works here because it makes the armor on that side look too narrow. It's all up close to the head and so doesn't stick off the shoulder itself as much as the blade on the other side, so he looks imbalanced.
Overall though there are some creative techniques in play here, and while some of these models could use further improvement they definitely work towards the goal they set out to achieve, that being a re-imagining of these characters using the new building style.