I find it odd you mentioned who would want to use gripstocks of manpads on a tank yet suggest that it's ok for bmp-2/3. I wouldn't recommend either.
The crew of the BMP-2 or BMP-3 don't operate the gripstock of the MANPADs, it is the troops that deploy it... along with rifles and machine guns and their own anti armour weapons etc etc.
If there is an air threat... and these days even in COIN situations that would be mainly drones and UAVs etc, then the gripstock might be deployed... if there is none or it is unlikely the gripstock might stay in the BMP and the soldier will just use a rifle.
I think the 2T stalker is was all done remote inside the tank. but as I mentioned a strelets type system gunner wouldn't be as exposed or more likely option SOSNA would be better.
I think the fundamental question here is... do you start making vehicles multi function...
On the older vehicles that means adding new missile types and also new sensors and equipment for those missiels (esp for SOSNA).
I agree SOSNA is a much better missile than any MANPADS, and with a 10km range can outrange most light aircraft launched anti armour weapons.
However I think there is also an opportunity because the new SPAAG system uses the same 57mm gun as the new IFV, so a sensor and optics sharing, and also improved communications that comes with the new vehicles suggests that most IFVs with their 57mm guns will already have organic powerful anti air capability anyway.
The air burst ammo so useful for use against aircraft... especially fragile little UAVs, would also be very useful against a range of ground targets, like troops in a trench with front cover but little to no top cover. Equally the ability to fire a round into the room of a building and have the round explode 2-3 metres into the room after coming through the window would be devastating...
rocket screens as they call them in uk (caged armour) was the solution as it was cheap effective
I remember a photo of a T-34 rolling into Berlin in 1945 that had an innersprung mattress with all the fabric gone and just the wire being used as protection from Panzer fausts... During conflicts they already fit their BMPs and BTRs with cage armour and extra armour kits, but you are talking about MRAPs and I am talking about armoured vehicles.
When the US entered Afghanistan they had little to no MRAP type vehicles... and then they squandered billions of dollars and bought about 10-15 different types of vehicles and tried to upgrade existing types to various levels of success. Now the focus is on big boy enemies like China and Russia they are dumping the vast majority of their MRAPS and going back to normal armour...
For real armoured vehicles, NERA or ERA, plus cage armour, plus APS should be enough... adding the ability of remote weapon systems to operate like CIWS is a bit redundant to try to stop an RPG attack in my opinion... as you mention no warning, short range very short flight time... I doubt most of the time the RWS would have time to turn to the threat.
Especially when the locals realise the RWS is attached to the commanders sight so it shows them where the commander of the vehicle is looking right now... when it points in the opposite direction is the time to attack...
Of course with more than one vehicle and perhaps UAV support they might have seen you and are looking in the opposite direction knowing the APS system will stop your rocket attack but the vehicle up the road in the distance is looking right at you waiting for you to step out...
The issue is situational awareness... in an urban area there are so many factors it would be hard... a high level of communication and cooperation is what is needed.