The Rescued by Itemreader may meet your requirements. Warning: there is M/M in the latter part of the story.
The Earth is destroyed by an alien spacecraft going off-course and crashing into it, completely shattering the planet; instant asteroid belt.
The other ships in the convoy attempt to salvage as many bodies as possible from the debris, and scan the brains and produce clones and implant the data from the scans. The clones are all of a similer age, early 20s, despite the originals ranging in age up to 75.
For some reason, female bodies found vastly outnumber male bodies found, so the mix is most unbalanced [how else to develop instant harem setups, after all?]; all seem to have been away from populated areas at the time of the accident.
Multiple clones are created, and placed in different groupings; this isn't evident at first, but in the second section of chapters it becomes clear this is the case. This allows for different developments to occur in regard to interpersonal dynamics.
The aliens are very hand's-off in their relationship with those they rescued; this is explained in the first chapter.
It's an interesting read. It was posted in 94 chapters, starting on 1/14/2007 and finishing on 4/16/2007, so as you can see it moved right along.
This was Itemreader's first story; he wrote a total of 7, with the last finishing posting on 3/16/2009. His last blog post was on 10/25/2010. Clearly, he's logged on since then, as none of his stories are Premier.