I like the fact that they're regarding T3 as a different timeline. The less said about that movie the better.
That said, this still doesn't sound like all that good of an idea. It seems like they're trying to play closer to Cameron's world than T3 did, but ripping off the first two movies piecemeal isn't the way to go about it. Then again, even if they branch out a little bit there's still gonna be problems. I don't see how the show can work without terminators being a major part of the action...but I also don't see how its going to tie in all that well with the mythos if new terminators are showing up every other episode and all the characters are jumping around through time. I don't see how you can maintain the balance.