I would love to have the Kindle Keyboard and Kindle 4/5 (original basic) with front lighting, custom fonts and boldness slider. I dream about this often.
My ideal Kindle:
Dark crisp fonts of the Voyage
Even lighting with no gradients
Warm light
Traditional form factor with page turn buttons from Kindle 4/5
Four way manual screen rotation, or auto rotation
Always have page numbers option available
Return of the progress bar (which can be turned off in settings)
Processing power of the Oasis 2 & 3
Ability to place what a user wants to easily access in toolbar/quick pull down. I would set mine up for easy access to X-Ray, Series Group, Oasis forward/ backwards page buttons, deep in the menus I would have GoodReads and Bluetooth.
Return interface to version 5.13.6