This isn't their best effort to ruin his legacy, IMO...The prequels just seem to lack the temerity of their other derivative crapfests.
You're not thinking "big" enough. If you really want to see DC crap all over Watchmen, wait until what happens if the prequels (and possible sequel) sell really well: there's no way DC won't break down at that point and find a way to do DCU/Watchmen team-ups, most likely in the concept of a weekly crossover "big event" mini-series.
If I'm thinking correctly, then they have already laid the groundwork for such a crossover. Isn't their a Watchmen earth in the 52-niverse? Though, I think they also admitted that it wasn't THE Watchmen universe.
I just think the prequels are a bad way to kick all of this off. As I said, all the backstory you'd ever need is in those original twelve issues. JMS said they were going to be true to the source material. If that is the case and all the backstory is already there then I don't see how these could add anything to the already existing story or depth to any of the characters. Save, maybe, Cooke's Minutemen. IMO, all of it will just read as flat derivatives. I give them credit for having the balls to milk this cash cow. It just strikes me as overly conservative in how they are milking this cash cow.
Prequels remaining true to the source material = boring
The third generation heroes: Nite Spectre, Lobotomy, and Laugh Track vs Ozymandias's army of time traveling Alie-N-azis from a parallel world = fun
