I agree heartily -- please keep this in place till 2.2 launches, that way those of us who missed it earlier can get some nice toys too.
If I go all-out this week with my 4 characters at 50+, I can probably "store up" enough reputation to have enough reputation saved up to hit Champion in 3 weeks, but bleh, it really shouldn't be necessary.
As to why this event returns while the Chevin scavenger hunt and the Rakghoul event haven't, this one actually has an in-game reason for returning but the others don't. The Cheving thing in particular was supposed to be a prelude to the Return of the Gree anyway, and they are now here -- as per the Terror from Beyond operation. (IMO, It probably wouldn't hurt to see a Gree-themed Flashpoint in addition to that).
I know these events must take a lot of planning and implementation work, so that one-off events will probably not be part of the business model from now on, but please don't abandon them!