Look at this one for an obvious example of how things are significantly altered.
Two-face's ruined side is the WRONG side. This will happen with any manga based on, or the basis of, an anime, a western comic, or a work of literature with detailed descriptions, if it happens to involve designs that are asymmetrical. Actually, it'll happen with any design that's asymmetrical, but it'll only be noticeable to people without access to the original with the above other versions.
Now being off-model could be considered a minor issue (although, it can carry information which is altered by the flop*), and won't be noticed by someone who's not familiar with the other versions/original manga.
But it points out the obvious problem - what's on the right in the original art is on the left, what's on the left is on the right.
Which has serious implications:
Things that shouldn't have to be redrawn WILL - clocks, or anything else with numbers; money; signage, badges, clothing, etc that has English (or, if the translators are serious, any other writing), real (or significantly designed) asymmetrical logos, etc, on it. (Notice how many of these examples are in the above excerpt - a coin, a police badge with writing, a number, a recognizable asymmetrical insignia (Riddler's ?s).)
There will be serious departures from reality, without significant redrawing (to the point of removing most of the original art) - almost everybody will be left-handed (except for those who were left-handed in the original); Americans will drive on the left, Japanese on the right; real geography and architecture will be wrong; police and military uniforms will be wrong - police badges or military medals and ribbons worn over the right breast, not the left, Sam Browne belts will go over the wrong shoulder, armbands will be on the wrong arm, insignia will be reversed (if possible, and not redrawn), etc; computer keyboards will have the numberpad on the left; and many other such things.
* As it arguably does in this case - Two-face's ruined side being the left was probably not a random choice. Though the significance of having the ruined (and, thus, evil) side being the left ('sinister') side is probably not consciously recognized by most people.