It would be nice to group items into groups for the filtering.
This could be done with a sign similar to the autocraft sign.
Maybe to specify the filtered items you could place them in the hopper so you don't have to include them in the command.
The filtering options could be applied with the command.

Examples:
We have a auto cooker for meat. We do have a range of fuel that could be used. We usually drop a few stacks of fuel into a chest that also allows us to drop raw meat in.
With the item frame we are limited when it comes to the fuel.
It would be great to be able to create a group with all our fuel options so all of them get accepted.

We have a huge sorting machine that sorts items in chests.
We can either have 4 filtered items or a small machine size.
Having 4 items would at least triple the size.
As we picked the small size we now can't put all 3 iron variants (bars, blocks, nuggets) into the same chest.
Having a group for this would make sense.
Same with armor or items we don't have many of (to save chests)

It's just something we thought about.

You can place multiple filters on a Hopper you know? And you could just have multiple of the same 'Linked' chests with multiple hoppers underneath that all point to the same furnace/chest.

If you don't understand I can provide some images of what I mean