In addition to the other points, imaginary numbers immediately added to the representation of things we could represent. Simply rewriting existing numbers in other ways isn't all that interesting; it doesn't add anything. We already knew there's an infinite number of ways to serialize numbers to symbols. Negative base numbers don't behave differently than positive base numbers, because "negative base numbers" and "positive base numbers" are artifacts of English and don't actually exist mathematically. There are numbers, which are written in different representations, but are not actually different entities.

So there's no possible way this could be useful for "higher dimensional math" or anything, because there's no entity being added here. Higher dimensional math already uses numbers. At most there might be one or two concepts that might in some manner if you squint hard enough could be better represented by negative base numbers, but even then the positive base representation would probably still be how people actually understood it.