Personally, I can see this being a good idea. However, there are some flaws in this idea.
The first one is obviously obtaining permission. Taking another persons mod and changing values to make it "less OP" will have issues. For example, the modder might not want anyone else to use their sprites for any mod, even if it is just a rebalanced version of it. Or they might not want their code being messed with, or their reputation ruined because someone else had to balance their mod.
The second issue is that parts might be powerful for a reason. There are a lot of futuristic mods out there and it's not a bad assumption that weapons, shields or armour from the future would be more powerful. Of course, there are individual parts that are OP, but I think in this case it's better to suggest balancing changes directly to the mod creator, either by telling them why the part is OP and how to fix it or giving them a modified file.