It would be nice to have another way of attaching “add-ons” to a product. With the current product “options”, say I’m selling an item with an optional plug adapter. If I have 50 of the product in stock, but only 25 adapters, the only way to indicate that currently is to create 2 options, with and without, and say that I have 25 “with adapter” and 25 “without adapter”. However, in reality, I have 50 without the adapter, and if everybody wants to buy without the adapter, it looks like I only have 25 of them available.
Having the option to specify “add-on” options would allow you to keep the stock of the main product separate from the add-on, and could also allow you to attach multiple add-ons to a single product without having to create a new option for every combination of add-ons (e.g. and adapter and a power supply), or a quantity value (e.g. you could buy 1 product and 2 adapters, preferably with the ability for the seller to specify a maximum quantity allowed per main product ordered.).
For now, I can make do with the existing product options feature, or just split the “add-ons” out to a separate product listing, but I figured it didn’t hurt to ask.