Pakistan maybe in negotiations for L-15 but those should not be coming to replace F-7PGs. F-7 P / Pgs are combat fighters (interceptors) whereas L-15 is dedicated LIFT. F-7 series replacement on role basis should be JF-17s.
Jeff bravo isn't a dedicated LIFT but a multirole combat aircraft with conversion training ability. However, Jeff bravo could have possibly reduced the need for a dedicated LIFT platform but not eliminated it completely.
if PAF is only looking for dedicated LIFT then off the shelf L-15 makes sense as the timelines and cost to develop a JF-17 bravo could be higher, That's just my opinion, don't know the actual cost of L-15 though.