It would be SUPERB and a huge time saver if we could upload geeklists in a text file. eg ItemType, ID, ImageID, Text. It would have to be a CSV sort of thing with text delimiters so we can upload Text with line breaks in it. Format could be STRICTLY enforced and the page that describes the format could start out with "Sorry, no admin help can be made available for this feature". It'd be nice but not essential if the format accepted nulls or zero for ImageID.
Just reject anything which didn't compute. By all means tell us why if you can but if you just tell us "file format incorrect" and the first row/column/value that breaks (remove all potential HTML markers in text) I'm sure those of us who would use it can get it right.
Uploading a list wouldn't auto-submit it. Just populate a list ready for further editing, review, and then submitting.
I don't know about everybody, but I'm sure quite a few of us die-hard listers use other tools to help prepare our lists. eg I have some data in a MSAccess file and use formulas and code to pull together some text for entry usually in Excel. Then I have to transcribe the list by hand to BGG... One. Number. And. Text. Box. At. A. Time.