Bigger file handling using file system api

Ace’s performance is fantastic for in memory document editing. It advertises 4 million lines as its limit. I’m trying to determine what it would take to be able to support >=12 million lines. It seems like using a filesystem would be necessary. What would it take to implement a file backed version of ace that used the experimental FileSystem API? https://developer.mozilla.org/en-US/docs/Web/API/FileSystem

I’ve barely started to look at ace’s implementation and am looking to get an idea of what work would be involved to make this happen. For example, I imagine the assumption that all data is present in memory is made throughout ace and that there would be a substantial amount of work in all facets of the library to be able to make asynchronous file API calls. Or is enough done in WebWorkers that the synchronous File API could be used? Would it be as simple as creating a FileDocument class that mimicked the Document API? Any thoughts on the matter are appreciated!