Thanks M-ATF, what would we do without you.
I could have sworn I saw a KAT-72 gunners sight in one of the T-72s in Maydayfire's video on another thread but I wasn't sure; its as clear as day in those screenshots though. I've never seen them on any of the T-72s on parade or in other exercises; it's about time if you ask me.
Speaking in regard to doctrine, I wonder if the Sheni-dar is designed to replace Jeeps, transforming motorized infantry into proper mechanized infantry. It's not a dedicated scout vehicle and it's not an IFV like the BMP (lacking protection and armament), or a proper APC like the M113 or Boragh (lacking the ability to carry a full rifle squad). Judging from the video it can carry four infantryman with a vehicle commander and driver which is more-or-less closer in equivalence to a Jeep then it is to an M113.
The compromise in features and size may be a function of strategic mobility requirements which is a particularly compelling argument in light of it's description as an ultra-light, highly mobile vehicle by Fars News. The small size may point to it being used by air-mobile units in the same manner as the BMD-1 or the BTR-D (the first comparison I heard about the Sheni-dar was towards the BMD). I'm not sure of how big of a demand there is for such a vehicle though. There are other forms of mobility though; smaller vehicles use less fuel, are less maintenance intensive (as a general rule of thumb), and can go over more bridges/roads/tracks/etc then their larger counterparts can. I wouldn't underestimate the importance of being able to reduce the logistical footprint as much as possible.
Notably, it has a lot more headroom then the Boragh/BMP.
Mobility-wise, it's atypical that the shock absorbers should be fitted to the front two wheels sets of road wheels rather then the front and the back sets. Other then that, the running gear is pretty standard; the four road wheels are aluminum, have solid-rubber tires, and are relatively small. The suspension uses torsion-springs attached to the road wheels which is standard on tracked vehicles these days, though there does appear to be a fair amount of room in-between the road-wheels and the track-return-rollers above them, which in theory could mean that the suspension is soft but I think the small diameter of the road-wheels prevents this from being true in practice.
I think that the choice to go with a large windows (presumably bullet-resistance) instead of periscopes speaks volumes about the overall doctrine. Windows are going to cost less than sealed periscopes during production and over the lifetime of the vehicle. The downside to this is that it creates a huge ballistic window in the frontal arc. It's noteworthy that neither of these designs represent any significant improvement from Iran's past generation of indigenous armored vehicles (compared to, for instance, the gap in capability between the M113 and the M1126, or the BTR-60 and the BTR-80). In terms of engineering sophistication, it's at the same level as the Boragh which was being produced 15+ years ago.
Wish I knew what kind of engine was put in it.
The Sarir on the other hand reminds me of a cross between a Rakhsh and a BTR-60. Compared to the Rakhsh, it has a larger engine, larger wheels, wider wheel-base, and a lower CoG, but it is still smaller and less expensive then a BTR - the most notable area of comparison being the number of wheels (four vs eight). Like the Sheni-dar, it's an APC-lite which might indicate that it's purpose might be the same - mechanize a rifle squad that otherwise be lacking any armor at all.
It's also worth pointing out that the 14.5 mm machine-gun is mounted in an awkward position directly over the seats which would make it difficult to use.