The editions are extremely lacking on hardcover. Generally there is only the paperback version. But rarely do I see an ebook or an audio book edition.

If I'm understanding what you're saying correctly, this is already possible. In the same menu where you can add a new read or edit the date of a past read, if you click into a specific read, there's an option to switch the edition you read, which would also change the format. (If you can't find the specific edition you want, you may need to add the edition to the site and then try again.)

That said, though, I'm not certain how the stats page handles different formats for rereads. So if you've already selected your editions as detailed above but the stats page is still weird, then yeah, one of the higher-ups would need to look into that.