You are correct in assuming this is Mark 3 based. But this is not a cheap alternative to the Namer ARV. They fulfill very different tasks.
Simply, the Namer ARV replaces the M88, and the Pereg replaces M113 maintenance vehicles such as this one:
By the way this new variant is called Pereg. It is a Hebrew acronym for Generic Armored Platform for maintenance units.
It will be used by Company-level tech units to maintain tanks and other AFVs, reducing dependence on light crane vehicles like the Rio trucks or M113s.
Of course, there will be an overlap with the Namer ARV, because the ARV will use its massive crane to assist others in lifting light weights like powerpacks and armor blocks, which the Pereg can also easily do, and use its sheer size to carry spares but they still fill different niches.
Pereg is also said to have a MEDEVAC capability, a capability which I do not know whether the ARV has.
The superstructure itself seems to add quite a lot of room in the Ofek, and I assume here as well. Perhaps more than the Namer affords.
EDIT: Pereg may not necessarily be able to lift a powerpack, and light crane vehicles' ability is in doubt.