I think there is a continuum from 1 MB all the way to 999 MB.
It is a value judgement of where is the cut off as to what will discourse support. Please make this value judgement and document it in the manual (currently it seems around 75MB). I have spent over 5 hours trying to figure this out since the manual or the forums made it seem as if large file uploads were possible with discourse.
For me uploading 100MB takes less than 5 minutes and more and more people are going to have fast upload speeds.
I dont mind starting from scratch.
In my opinion discourse product should support large file HTTP uploads out of the box without trying to do resumable or anything fancy like that. Obviously its just one user so feel free to disregard it completely 
Obviously a product designer has to say NO to develop a great product
As you make your decision as to what will discourse support please take my use case as one more data point.
I use discourse as a internal corporate forum and in my work I have had a need to upload files of upto 200MB.
Is there a technical limitation in supporting large file uploads without anything fancy like resumable etc ?