Shimud, OK - sorry buddy for posting "old" news

!! I do not think that any others have been delivered so far, but to my knowledge all original build F-16s for the PAF are to be returned!!
You are right about the increased stress on the airframe regarding aggressor work. But You might remember that the USN that operates some of these F-16s as aggressors have flown a short period of time of only a few years and the individual airframes were brand new when they entered service.
The Edwards based test/chase planes have even fewer flight hours and are not structurally stressed in the same matter than the aggressors!!
So - yes they are used airframes by now. But in comparison to other airframes - the AMARG stored one for example - these planes are virtually brand new.
No, the MLU modification does not offer any structural replacements as such. There is, however, some programs in conjunction with the MLU that serves the airframe. Falcon STAR (Structural Argumentation Program) is one such modification. The European MLU aircraft along with many Block-25/30/32s in the USAF can be recognized by several "scab" plates on the fuselage witnessing a structural upgrade program.
I, however, suspect that these originally PAF build airframes have internal structure strengtheners like the Block-50/52 series, as they too were build in the early 1990s - at the same time as the majority of the Block-50/52s.
Block-40 export versions for Egypt and Bahrain have this very same internal strengthening.
Hope it helps.
Many greetings,
Henrik.