Like I said, the Grad is outranged by modern long range GPS guided artillery even when modernized, and the Smerch is just too expensive to use in large enough numbers.
Smerch is not expensive.
Uragan is in the middle not offering anything special... Grad is cheaper and easier to produce in large numbers and for the battlefield role of hitting targets like an artillery rocket is supposed to it is rather good. Smerch is heavier and has much longer range than the Uragan could be adapted or upgraded to have and with a bigger payload that it can deliver.
Uragan rockets could be upgraded but they are not going to be better than upgraded Smerch rockets and the fact that upgraded Grad rockets have comparable reach in terms of range and make up for its smaller payload by having 40 rockets per launcher means the Uragan is the expendable one.
I also think you overstate the difficulty of making the 220mm rockets.
They said they will phase out Uragan rockets, they didn't say they would stop making TOS and TOS-2 rockets which are also 220mm calibre.
They already have the propellant and composite casing technology for the 122mm rockets. It is just a matter of using that in a larger diameter rocket. They will eventually use those materials in the Smerch as well with 300mm. So adding them to an intermediate rocket isn't going to be much of an issue.
I don't think anyone thinks they can't do it, it is more a case of choosing not to.
They also decided to phase out the 122mm calibre guns in the form of the D-30 towed gun and the 2S1 self propelled artillery vehicle... the payoff was that it was rather similar to the 100mm and 120mm and 125mm weapons already in use so eliminating an entire calibre made sense... the 122mm gun could be replaced by 120mm gun/mortar weapons in towed and self propelled versions (2S34 Hosta) which could fire 120mm mortar bombs of east and west, 120mm shells with propellent charges to 13km compared with 15km for the 122mm gun, and the 120mm gun/mortar could also fire the 122mm guided missiles called Kitilov, so for a small reduction in range they could eliminate an entire calibre from their inventory. The 120mm shells were similar in power to the 122mm... 2mm is not much of a difference. And there were light mobile towed 120mm gun mortar mounts that could easily replace the D-30.... but after experience they seem to have decided to keep them.
They might decide down the track to keep using the Uragan missile perhaps... the 15 tube pallet means the two pallet vehicle could carry 30 rockets ready to fire which is rather more potent that Uragan ever was with 16 ready to fire tubes.
Unless they decide that that truck with two pallets for 220mm rockets could replace TOS which also carried 30 rockets didn't it?
The new TOS is truck based and unifying the TOS and Rocket artillery trucks together into two vehicles... one carrying one pallet and one carrying two pallets of 6 x Smerch rockets, or 15 x TOS rockets, or how many 122mm rockets?
But then small light vehicles with 80mm air launched artillery rocket pods seem to be of interest too...
In the middle term, I think they need to make a vehicle roughly the size of the BAZ truck, with a modular system which can optionally carry various kinds of rockets, and maybe even cruise missiles just like the Brazilian ASTROS system.
I think for targets deep in enemy territory that ramjet and scramjet powered missiles that can manouver and hit point targets will be rather more cost effective than volleys of unguided rockets... having 40 launch tubes makes no sense if you are firing one rocket at each point target and then driving away to avoid counter battery fire.
Having a launcher with 6 missiles makes more sense and you could launch all 6 missiles at individual targets if you have the target data at the time of launch... this will also help complicate the task of the enemy air defence.
Furthermore at that time the various belorussian firms like MZKT can be better integrated into the Russian production.
Russia would benefit from more production capacity... and more workers too....
And would not be throwing away the lives of their new citizens on adventures to steal money like the west does all the time.
The INF treaty is gone so now Russia can work on intermediate range missiles, whether low flying subsonic cruise missiles like the new Kh-50 cheap subsonic land attack cruise missile designed to be carried by light tactical fighters and potentially ground launched too with a range of 1,000 to 1,500km or so with accurate terminal guidance, or perhaps a ramjet or scramjet powered semi ballistic missile perhaps with different versions with ranges of 250 or 500 or 750 or 1,000 or 1,500 or 2,000 or 2,500km range with different payload weight options and ramjet or scramjet propulsion to evade enemy air defences to ensure it makes it to the target... mass production would be cheap and fuel would be cheap because it would not need to carry lots of oxidiser because it is a jet engine.
You might say... cruise missile are expensive... no they are not... ramjet and scramjet engines have no shafts and no blades and few moving parts and are essentially an air breathing rocket jet engine. The terminal guidance would be needed for a ballistic rocket if you actually want to hit targets but a jet powered manouvering missile would be more likely to actually reach the target. Guidance and propulsion will probably be cheaper.
They could make air launched versions too if required and produce them in enormous numbers.