I am sure you are aware of most of this.
Since you posted your results, I hope this answer may help to work on this.
That is honestly a pretty good start already, especially if you have personally tested:
read-only USB transfer
NCA/CNMT...
I prefer my slop open source
I tested this on my switch so far :
read-only USB transfer
NCA/CNMT decrypt test
NSP install from SD
USB install through dbibackend
I'm actually burning my work's leftover weekly token during the weekend. :evil: I...
I started throwing all my tokens at re-creating an open source version of DBI. For now, it can install .nsp, .nsx and connect to dbibackend for file transfers. https://github.com/mrbeige1/open-dbi