Hi,
We actually redid completely the variants management system a few months ago. So most of the problems you saw on other threads with the variants are already solved.
Regarding the updating of variants in bulk, you can already do this thanks to the mass actions system in HikaShop. You can access it via the menu System>Mass actions. You can have filters to update only variants with some characteristic value, only for one product, or a category of products, or for all of them, and then have actions, to change some values of the mass actions.
For now, the mass actions system doesn't support updating/adding images, but that's on our todo list.