I have cupboards as well, and unfortunately I haven't been able to find any such kits that will fit the dimensions (narrow depth). Bins would probably be your best bet.

The dead zone is where you stash stuff you rarely use. That corner is where my chafing dish goes....since I only use it a couple of times a year. Bins are your friend. :)

I use bins also. The multi purpose bins from the container store work well.

You might try floor mounted drawer slides to provide pull out drawers. Corners are hard, perhaps smaller Lazy Susans. Look at some sites such as "familyhandyman.com" or Rockler, they have many options for cabinets space.

We have a corner like that. When you pull open the door a quarter circle pulls out with the door. When closed, the shelf part goes back into the corner.

Will you be putting doors on?

It has doors, they're just removed for the renovation. The bottom section is a 9.5" gap and about 30" deep. So a series of baskets/bins may have to be the solution.

Plastic bins and plastic trays work well and they are budget-friendly.

I have one too. Its called a blind corner cabinet. There is hardware/inserts for this. but since yours is odd size, they won't help. I keep my large roasters etc there, but there are times when something gets back there and falls over. You could put a divider there so its only accessible from the larger door on the right. Vertical dividers could be added to the smaller cabinet to house trays and cookie sheets.

You can buy a flashlight and put it in the cupboard ready for you to start looking and fishing. I recommend lining the shelves with white shelf paper, the kind that is easily repositioned and easily removed.

There isn't another opening other than that tiny 9.5 x 8 hole so roasting pans and the like aren't able to fit. It's just a poor design all around.

Now I see the narrow place with no other access: it's on the bottom, not the top. I recommend storing something you can put in a clear plastic bag back there. Yank on the plastic bag, not the individual items. Extra plastic spoons, cake decorating supplies, anything you don't use more than every month or two. In the accessible spot, a stack of bread pans will probably fit.

I don't know why there is a partition on the bottom and not the top. I would partition of the small side and make it a pull out. Here are some ideas: