Peculiar and redundant project that keep surviving, imo, only buy political weight of regional Tatar government who kept it alive during the 90's as well, by financing development and production.
Not redundant at all.
If you cancel the project, which already has aircraft in service you already have to spend money replacing the foreign components in the operational aircraft, so you are going to Russianise the existing aircraft anyway.
Cancelling the project means you then need to spend money to convert all the factories and producers to change to produce aircraft you will be making, which will take time and wont be free and will be added to the costs of stopping production of the Tupolevs and converting them to Yaks or Sukhois.
In other words there will be a long period where they wont be doing anything at all while getting ready to make different types while costing money.
Continuing to make Tupolevs means the existing fleet can get Russian parts and upgrades to improve their performance, and testing and work can be done that does not effect the work on the MS-21 or Superjet, so all three can run in parallel getting planes that Russian or Russian friendly airlines can use instead of foreign types from companies that hate Russia.
The Russian military does not need super advanced composite airliners with the super low cost flights, the Tu-204/214 is just fine as it is and will be even better with all Russian components and systems. There are plenty of Russian military types that need replacing including the Il-20 and Il-22 in elint roles, as well as Tu-154M and Il-38.
They could also develop the Tu-330 transport plane that is largely based on the Tu-204 and is a 35 ton payload transport plane.
A light AWACS and inflight refuelling model would be useful too.
The way this is being done is by replacing Western components with ones which were originally designed for the MC-21 modified to be used in this aircraft. Which is one reason why I think this project is a bad idea. It is consuming scarce resources which would be better put to use to finish the more modern MC-21.
Standardisation is a good thing. Production capacity of the parts used in both or all three aircraft should be funded accordingly and capacity for production increased.
Having said that, after claiming they needed just over 1,000 new aircraft by 2030 they have since revised the number down to just over 800 aircraft, so the requirements will be changing over time anyway, so planning and development need to be flexible as well.
Worst case scenario 20 aircraft a year they could produce them only for the Russian military and that would allow them to upgrade their MPA fleet of aircraft and Intel aircraft and VIP aircraft over the next five to ten years and not one airliner need be made.
If you cancel it, then when the Russian military starts placing orders that is going to be even more pressure on MS-21 and Superjet production.
Import substitution means Russian computers and cabling and equipment manufacturers getting orders and producing stuff... which is the only way for them to grow and develop their businesses.
There will also be aviation systems like weather and other systems based at airports as well as command and control systems for air traffic.
The fact that they have three aircraft is a good thing, while extensions and reductions in aircraft lengths will allow other niches to be filled relatively quickly and efficiently... and with Russian types too.
Like I said before, if Kazan wanted to manufacture civilian aircraft they could have made a small regional jet transport aircraft. There used to be a Tupolev project for one. And there is no such aircraft right now. Instead money is spent on duplicate projects.
Another alternative would be making military transports.
The Tu-330 has 70% commonality with the Tu-204... and is probably more urgently needed than most other types as a 35 ton payload transport between the Il-276 and Il-476.