Observably and experimentally, it’s so hard to test powerful gravity fields. But theoretically, if we could confine and increase a portion of matter into a far more dense state, we should be able to create increased gravity - I think that’s possible, but it would take insane energy and you’d have to control it to a point that it doesn’t turn into a giant explosion; seems very probable and should be conducted in space…just to be safe.
But, is your thinking that if we have a net zero energy universe, it should not have a big bang, or just that a net zero may have originated differently from a big bang? I’m just curious.