Some thoughts / questions I have about on-page optimization:-if meta keywords are no longer used in the algorithm for search engines, do we even need to bother with them at all? What purpose would it serve? Having the keywords there may just tip Google that you are trying to optimize those keywords...I may remove them on some pages to see what it does to the rankings-if there are any keywords you list at the bottom footer / index, this may be seen as over-optimization as well.-do you think using keywords that also happens to be your Category name or Product brand name is considered being over optimized?
Meta keywords contribute nothing at all to SEO so there's no point in using them. The only thing they contribute is a possible risk in over-optimization that you mention. It's only minor, but seeing there's no benefit, don't use them.
The use of meta keywords make it dead-simple for competitors to see what you're trying to optimize for.