Do they plan on upgrading the BMP-2s?
I think this is all about testing... they have three or four new turrets and they want to test them on everything.
The BMP-1 has a tiny single man turret so only the smallest turrets could be tested on those... maybe the Kliver turret or something similar that was used on the BTR-80A with the 30mm cannon.
I would presume they will pick the turrets that make the best sense for that vehicle and what they intend to use it for.
They might have all the turrets mounted on different vehicles... remember there is also MTLB and BTR vehicles as well as Typhoon vehicles and arctic tractor types as well that might use turrets not suitable for the army.
The Au-220M is a dual mount for river boats and support ships too.
Also regarding the BMP-3 turret I always though that all it needed were some better ATGMs and some anti armor rounds for the 100mm, perhapse with upgrades it could fire APFSDS like the new dual pressure 57mm.
The Arkan is not a bad missile... relatively fast and with a 5km range it would get to a Bradley well before the Bradleys TOW reaches you... but you can drive with your beam riding missile while the Bradley needs to sit still while guiding its missile.
With the new EO guided missiles they are introducing I am sure a new EO guidance system could be developed for the 100mm rounds that could become diving top attack missiles... the BMP-3 certainly has no need for anything much bigger... in fact small launch boxes on the sides of the turret with Bulat missiles might be interesting, but its primary use would be against enemy infantry and enemy infantry vehicles so the 100mm missiles and 100mm HE rounds should be excellent.
The HE round is all bomb with a small stub propellent case, so in terms of HE performance it is comparable to a tank round while taking up a fraction of the internal space for storage.
Now, the main question would be: how those different models would be divided into a single unit?
They would not.
As the new vehicles of each type are introduced they can displace older models, so for instance, the first round would be to replace the T-90 tanks with T-14s and the BMP-3s with T-15s and the BREM engineer vehicles with T-16s and the MSTAs with Coalitions... then as newer Armata based vehicles complete development they can be introduced to Armata brigades or divisions, with the previous vehicles cascaded down to other units.
For a lower level unit they might have Kurganets vehicles so until there is a Kurganets with a T-14 turret that unit would retain their T-90s probably in upgraded AM form, while the different versions of Kurganets that are selected for use enter service and replace existing models.
Obviously as this process continues the top stuff from the top units will be either cascaded to lower level units or may be upgraded with new turrets and put in reserve for the top units to use in situations like Syria or peace keeping roles where they don't need their best stuff.
And the same for the Boomerang and Typhoon, though being lighter and cheaper and more affordable they should be able to make those fairly quickly and easily and they might form the majority of the army because they are so mobile and much cheaper to operate.
This will mean that over time all the BMPs and BTRs and BRDMs and MTLBs and GTSMs and old T series tank based vehicles will be withdrawn and replaced in their respective units by Armata, Kurganets, Boomerang, Typhoon, and Arctic tractor types, leading to logistics only needing one set of engine parts and replacement engines and wheels/tires and tracks and transmissions.
Remember in the current units there might be BMP based support vehicles... but ironically there is BMP-1, BMP-2, and BMP-3 and they all have different tracks and wheels and engines and transmissions, so you might have a BMP-3 IFV, but the engineer vehicle might be BMP-2 based, and the Ambulance vehicle might be BMP-1 based... you might have 3 or 4 recon and command vehicles based on 3 or 4 different models of MTLB... the original MTLB is very old, but the MTLBu and the MTLBM and other variations are still in use.
The MSTA is based on the T-80 tank with a T-90 engine fitted, so the benefit of commonality of parts has only be improved over time as upgrades to the T-80 tanks and MSTA artillery vehicles have centred around unification of parts with the T-72/90 series...
There would be just one model for each battallion, one for a each company or would them be distributed up to the lowest possible level?
It is hard to second guess, but they might go for the 57mm Au-220 gun mount for Armata T-15s for the extra anti armour power, but they might go for the Ephoch 57mm grenade launcher in the lighter vehicles because it still has a 57mm grenade launcher with an excellent HE bomb and a useful looking APFSDS round too... or they might decide the Bulat missiles are good enough together with the Kornets and that a 30mm cannon might be good enough.
They might decide the 30mm Ephoch turret is excellent for the Typhoon and have the 57mm AU-220 gun for the "tank" version in a six wheel configuration.
For the Boomerang they might decide the T-14 turret for a tank vehicle and a Sprut turret for a light tank alternative for some roles.
They might even mix it up... lots of decisions to make...
From the sound of things the Ephoch turret uses AI and the laser complex called Quarry to find targets with each sighting EO complex so the commander and the gunner can independently engage targets on their own if they need to, which is rather new and sounds very video game like.
For a vehicle like BMP-3 that sounds rather interesting with two bow machine gunners also able to lend a hand engaging infantry or even drones.
They are at the moment upgrading even BMP-1, BTR-82, MT-LB and even Akatsja howitzers
The turret ring of the BMP-1 and MTLB are likely too small, though for the latter they often have a rear mounted turret over the troop compartment.
With these being non penetrating turrets they might still need the turret ring width to absorb any recoil.
It will be interesting...