I've always found the motivations of the Neimodians to be not very credible. If all mention of "trade disputes" could be removed and replaced with some more aggressive motivation (expansionism, a stab at galactic dominance, an attempt to cultivate slave labour etc. etc.), I think the film would mesh more easily with the style of the original trilogy while making the Neimodians more threatening villains.

Would you consider dubbing the Neimodians or using subtitles at all?

How about completely changing the nature of the Federation, their motivations and their origins?