I think something like zerospinboson is suggesting could work. Since this is a "test the waters" concept the publisher could simply offer prospective authors the option to place their manuscript in ebook format and if it sells well they will develop it further and release it in printed form. No advances; no editing; no marketing; a generic cover art overlayed with the title (
like this).
If the author can sell 5,000 copies then the publisher can invest in advances, editing, custom covers, marketing, etc.