Hmm...I haven't exactly been following the J-11B program...could you tell me how long it it took?It's just not possible for Pakistan to get the modified version based on the time frame they are talking about. It will take until at least late 2010 for the production on J-10B to start if we go by the flight test timeframe of J-11B and JF-17 04.
As for the JF-17...then that was a first flight. That was the first time development of a "new aircraft". No JF-17 existed before so they had to test the aircraft not just the modifications.
This on the other hand, is an "improvement" over an existing design. Honestly, unless there is a significant change in its aerodynamic behavior...I don't see how a JF-17 style DSI + Tail-housed ECM suite + FLIR would cause any delay beyond end 2009/ start of 2010....or the speculated AESA radar for that matter.
You do not have to build prototypes to go through fatigue testing, weapons integration, etc all over again. Most probably flight testing and engine performance and that too not to an extent of a new plane.
As for fitting European avionics/EW suite, that's exactly the point, China probably wouldn't want Pakistan to do it. Unlike in JF-17's case, Pakistan doesn't have ToT for J-10.
That looks more like your wish/fear than a good enough reason. I talked specifically about radar and ECM...and honestly, you even need a complete ToT to do that.
But for PAF to go for western stuff, one has to assume that China either doesn't have or isn't willing to sell stuff to meet PAF requirement. Then again, there is no proof or even a hint of China denying or downgrading the J-10 they will sell to Pakistan. That is purely your opinion/hesitation.
Let's not go into this until there is some evidence that points to this as all this is pure speculation. But just to put the perspective right, the source you quoted (pakdef) also mentions the M-AESA radar.