Create a Bulk editor for Shopify site

We need to easily add and manipulate our list of variants. Our site sells printed mobile phone cases and we have to add to the list of cases available. At the moment this has to be done on a product by product basis. Vela offers a bulk update but is riddled with issues. In a nutshell we need a bulk editor but primarily just for the variants to enable us to change one list and apply to all products.

We would also like to be able to have conditional drop down menus on our product variants, i.e.
First drop down option: Apple or Samsung
Second drop down option: Would only display Apple OR Samsung according to choice made in Option 1
Third drop down option: Case finish, matte/glossy/tough

We need to be sure that should we make any changes, themes etc. this modification would still work.

Budget tbd.