The only big thing that matters for WT is the Irbis Radar, but all ESA radars are in a nerfed state from the get go anyways because Gaijin can’t properly model it until everyone gets one.
Avionics that matters irl like ILS, Navigation, etc doesn’t matter in game. As for weaponry, there’s multiple aircraft that can carry modern weaponry but can’t ingame because of balance, and that’s totally fine
The upgrade was for the SM2 to use as many component as posible of the Su-35s. IRBIS its more powerful so you need engine that produce more power and its a lot more powerful it work at 10kw with 20ish kw peak. (These are some GaN numbers). Its also Lighter than BARs that weight 650k. From a old vid posted here. Early SM2 are just SM with more ground attack weapons. Because AL-41F1S fan diameter is 3% larger than the baseline AL-31 increasing from 905 mm to 932 mm. It was being tested. idk the date of the video is But it shouldn’t be a problem now because Russia have 177c engine that was show on Zhuhai. That engine produce same thrust as AL-41 but with Al-31 dimension so it can be use on all AL-31 aircraft. It have lower fuel consumption and more life time 2000vs 6000. Unless IT was just a prototype engine that isn’t ready for production. WHO KNOWs.
What its funny. At some point Su-35s was cheaper to made than Su-30sm. 27m to 30m. Because of the western component on Su-30sm.
Actually when I think about it, I wonder if Gaijin can magically find a late production variant with an 31F-M1 fitted. That would be good enough even without resorting to the AL-41