And what happens to all the Russian made Su30 munitions if you switch radars? How much time and money will it take to re-integrate all those legacy munitions onto the new radar?
And after all that effort, just how often do you want to hang PL15s on your Su30s on strike missions? Bear in mind that those PL15s are significantly heavier than PL12s.
So, I agree that upgrading Su-30s with PL-15s probably isn't worth it, but don't agree with the reasoning.
1. I think integration of PL-15s on older 4th gen aircraft lacking AESAs is viable, because going forwards I expect cooperative engagement to be the name of the game. Giving Su-30s PL-15 capability will not give them the ability to guide PL-15s themselves, because they can be guided by friendly 4+, 5th gen aircraft. That is to say, the Su-30s should be able to continue to utilize its current sensors and existing weapons suite (including whatever stocks of Russian weapons they have left) -- if they wanted to add in PL-15s it should not compromise the rest of their weapons availability, because PL-15 upgrades could conceivably be made with only datalink upgrades rather than overhauling the entire sensor suite.
2. Su-30s are not a dedicated strike aircraft as operated by the PLA, they are very much multirole in the same way J-16 is. Giving a multirole aircraft a more capable A2A weapons suite is very much sensible.
I also want to clarify the A2A capability of the Su-30 in context -- for a period from the early to mid 2000s, the PLA's Su-30s were easily the most capable A2A aircraft they had by virtue of them having a reliable ARH BVR capability for the first time with a decently capable radar. Even now, today, they are not operated exclusively as strike aircraft in the way JH-7/As are. They remain multirole aircraft.
But... There is a midlife upgrade you almost have to do anyway and J-16 sub-systems are already there! Those munitions have a shelf life, too which I am pretty sure shorter than Su-30 airframe lifespan.
... Continued from above.... the reason why it
doesn't make sense to give Su-30s PL-15s, is because of priority.
At present, priority for new PL-15 production obviously would be first going to new build 4+ and 5th generation aircraft -- i.e.: aircraft that can guide PL-15s with their own fire control systems. Given the number of new 4+ and 5th gen aircraft being delivered per year, I suspect PL-15 production is probably going to be prioritized for them for a while yet.
That is to say, I doubt older non-AESA 4th gen aircraft will receive PL-15s and the requisite datalink upgrades until PL-15 production capacity is significantly expanded into the future.
In the case of Su-30s specifically -- those Su-30s were flown very, very hard from when they were delivered to now. There are probably not many airframe hours left on them, I expect them to start being retired by mid this decade.
I very much doubt the Su-30s will get a mid life upgrade, because if they don't do a deep structural overhaul of the airframes, a mid life upgrade of weapons suite and avionics suite doesn't make sense -- and on balance, I suspect it would be easier just to order more J-16s which are much more compatible with the overall PLA infrastructure and logistics tail as well as substantially more capable (or if they don't want one for one J-16 to Su-30 replacements, they have J-10Cs and J-20s that they can choose to replace given units, as well as carrier based and land based J-XY production that will begin from after 2025).
So, IMO, given the likely retirement of Su-30s looming just on the horizon, giving them upgrades to accommodate PL-15 and giving them PL-15 stocks just doesn't really make sense.