This question of mine got marked as primarily opinion-based. As I couldn't understand why, I asked for clarification in the comments, but received none. I do agree with @kingledion that it might be a tad broad, but opinion-based simply does not make any sense. Would anyone care to explain the reasons?
I would tend to agree that the question is not opinion based. The forces mentioned are science based and therefore a non-opinion based answer can be reached based on what we understand these forces do in the universe.
Where I think your questions has problems is in two places.
Discussions on the extent/range/power they have would likely be opinion based. That is for the creator to decide.
It is far too broad. The necessary detail on each force would pretty clearly make each a question in its own right.
I will not vote to reopen the question. If it does get reopened I would VTC it as too broad Its not that the question cannot be salvaged, rather there are answers already written against the question as it exists and it would not be appropriate to change the question at this point. Invalidating the answers already written is a bad precedent to set.
I would suggest that you write questions for each force.
Clearly limit ranges/power levels for each force, i.e. the gravitational power will be limited to non-planet destroying levels of power. Considering we are talking about humanoids altering physical reality there is no non-opinion based answer to "how powerful can they be"
Once you limit the powers answers can focus on what the powers would allow the superhumans to do.
I think the question is exactly opinion-based. It is asking for answers that look at a given problem and brainstorm possibilities, and then the author picks which one he/she feels will create the best story.
Is that a bad thing on WB? Ah... there's the real question. Opinion-based questions on most Stack Exchange forums are bad things... there isn't a real answer. On WB, that brainstorm of opinions is often exactly what the question is trying to elicit.
Look at the "four forces => powers" question linked in the OP... the accepted answer makes up some rationalization for distance impact in the Weak and Strong cases. It's entirely opinion-based whether that's a good rationalization or not, but it is also exactly the type of help that the author was asking for.
I looked at @James answer to this meta-question. I think his opening paragraph is fundamentally flawed. When asking about hypotheticals, questions can either be answered with "probably this" or "possibly this". When it is "probably", we can find a best answer, not really opinion based. But when it is only "possibly", that's opinion, pure and simple. Splitting the question into 4 parts would just ask for four different opinions.
As I mentioned elsewhere in meta this morning, there's a tag on codegolf.stackexchange.com for questions of [popularity-contest]. They specifically created this tag for questions that are going to be voted up based on opinion. I think WB might look to that as an example. It might serve us better than trying to close opinion-based questions.