[Sabardeyn]

I cannot imagine a way to implement something like this under calibre's current file structure without entering them as multiple books. You are looking for a one-to-many database function and it doesn't exist in calibre at this time.

Kovid did mention altering the database structure to allow one-to-many situations, but I cannot recall if this was for a specific aspect only (multiple covers, editions, formats, reprints, etc), or in general throughout the database. I do recall Kovid mentioning it was a low priority project as other aspects of calibre would have to be substantially altered before this could be made to work.

At least, that is the overall impression I got, I might have misunderstood.

Despite the above, I'm not sure that what you want fits within the overall workflow method that calibre uses. My limited impression is that calibre is meant to take whatever original source ebook format you have and, on demand, to convert the book to a format that your software or hardware ereader can view at time of transfer. This means that ebooks are always as capable and functional as Kovid & Programmers, et al, can manage at the time of conversion. You always have and can re-convert as needed because you always have the original ebook file as the publisher released it.

What you are asking for, in effect, is that a book be converted either at the time it's added or on demand. The resulting ebook format would then be retained indefinitely - losing the advantage of any newly programmed conversion engine upgrades. Additionally, while hard drive space is inexpensive, their is little need to have multiple variant copies of the same ebook, differing primarily on screen resolution and CSS. (Alright, that might be oversimplifying things, but...)

Lastly, and I'm not sure I read this part right, but if you're getting rid of the original file, you can never reconvert. You're going to have the artistic problem of a "copy of a copy of a copy" with it's degrading quality. Particularly if you discover much, much later that their was a problem in that first conversion. Poorly converted ebooks tend to waste CPU cycles, causing slow book loading and page turns as the ebook's vague commands and structure are interpreted by the viewer's engine.

I think something that might make more sense with calibre's current functionality is a Load/Save Output Settings function. This would allow the various settings from the Preferences>Conversion section to be imported and exported, swapped as needed, when a user has multiple devices. In this manner all of the negative issues I mention above are resolved with minimal work by the user (after initial setup).

I'm not sure how many users would find this feature useful however.