1-3. You still need to know the word list but it could be changed in a way that doesn't depend on a fixed length word list like the algorithm Electrum uses
4-6. This can also be implemented but it would increase the number of words and the result will no longer resemble a normal BIP39 mnemonic.
My idea was an attempt to end up with a result that doesn't look any different from regular seed words.
I need a way to store more information than just the seed words. For each wallet, I figure I might need upwards of 1000 characters. Possibly I'd like to store multiple wallets all at once. So looking at maybe 5000 to 10000 characters. 10 kb. I need to be able to print out an encrypted image on a piece of paper. That would be my cold storage. When I'm ready to redeem, I will scan the image back in and decrypt its contents. And recover the original text file containing all my important seed phrases. I think this would be more secure than putting it on a flash drive since paper can last longer. Hundreds of years. then only problem is that you can't really use qrcodes for that. they would literally be huge.
Or i might just have a need to encrypt a text file containing 1000 private keys. That might require 2 pages.
You would not be able to use regular steganography to do that. You can't rely on most printers and scanners to be able to detect it. You would have to store the images on usb or other digital media.
Here is a basic steganography app:
https://github.com/computationalcore/cryptosteganography
Give it a try and see what you can squeeze into an image that you can scan later.
-Dave