Quite a few topics dealing with USSR issues, but i'd like to add another angle (i hope). What if the purges are not that destructive, i.e. they kinda focus in eliminating real or perceived top class (top as in military and party top) undesirables, without going all the way down to destroying the very structure of the military, and creating havoc in industry and economy, i.e. no prison based OKBs and all that.
Going from that, how could the military be better prepared for WW2? (this mainly big boy stuff). I did read some older topics on roughly this theme, it was mentioned some army brass had ideas such as tank armies which were dismissed, at least until WW2, not holding so many forces so close to the borders would have spared a lot of them destruction and capture (btw as known, some theories say that really the disposition of forces only point to Stalin preparing to attack himself, maybe in July), other helpful things being more radios for tanks, prehaps better attention to keep those 20,000 tanks (maybe a tad bit fewer) in better availability, and of course better overall training for the soviet soldier (air, land or sea) if possible etc.
I was thinking perhaps putting the I-180 in full production in 1939/1940 would probably give VVS several THOUSANDS of these in 1941 given soviet aircraft production rates. I kinda like the I-190 too but probably not worth it, though still better than the I-153 which was in production until 1941 iirc. Based on what i read the thing is about equal to Bf-109E, still a big step from the I-16. Probably this will make the I-185 also enter production so the Po-1 and Po-3 (my ATL designations) would replace most or all the Lavochkins as the war winning fighters. Maybe they can also adopt schwarm tactics as they should know about them from the Spanish civil war. Or how about a better KV, in OTL it had the same gun as the T-34 so no real advantage there, only being more complicated and heavier plus had less mobility. It appears they could have an 85mm (F-39?) or even larger gun (107 mm F-42?) on it as early as 1940/41, that would shock the germans even more. Also personally that KV-2 really scratches my brain, wouldn't it be better to just make the monster a proper SPG and not put the gun in that grotesque turret, sorta like that SU-100Y? Then you can have the SPG lineage evolving into something similar to the OTL SU-152, while the tank lineage evolves into something like the IS series.
Given all this, and assuming a better performance of the Red Army in 1941, does the massive industry relocation takes place, or at least have it on a smaller scale with less disruption? Perhaps one can have the (hopefully fixed) AM-37 in production in 1941 powering the Tu-2 and MiG-3. I know about the end of production for the MiG-3 in 1941, perhaps in this TL the need for Il-2s is not THAT pressing so the improved MiG-3 models could be built until 1942 or 1943, so you have Tu and Pe light fast bombers (i would have the Tu-2 replace Il-4 asap), Po, MiG and Yak fighters and Il-2 sturmoviks, and preferably some more Pe-8s too.
Anyway, just some ideas, would love to hear others.