If I were in charge, I wouldn’t put much effort into this, except it was a side effect of some other bigger feature.
I’ve also been using messenger apps for my personal notes and a bit of storage, and I’ve come to realize that it’s best to search for specialized tools instead.
A messenger app should be about messaging first.
I know it takes effort to find and get used to new software, but still.
For media storage I’d recommend to try Immich and its alternatives. For personal notes: Obsidian and its alternatives.
I’ve even had an idea to put such recommendations to the “Saved Messages” section in Delta Chat directly.
As to file size transfer limit, see this related topic Smarter message size limit.