They added the ability to use binary keys. The only limitation is that the entire key can't be 0. I hacked together something to allow UModel to use them:
It's pretty poor, I didn't send a pull request as the GUI key form will not work with them. If you start at the command line with -aeshex=key it will work.
Current key for fornite is 2c-cd-fd-22-ad-74-fb-fe-e6-93-a8-1a-c1-1a-ce-57-e6-d1-0d-0b-8a-c5-fa-90-e7-93-a1-30-bc-54-0e-d4
The implementation above ignores non-hex chars, so hyphens aren't necessary.
Key for Fortnite, but must use the horseit umodel fork to be able to open it, due to aeshex key difference in the programs...