My feedback on the show is....something seemed to go wrong when they created the AI speedforce, whether it's how they built (materials used) or the way they used nash as a organic conductor.
my guess nash dna is linked to wells, and the real wells is linked to thawne because when thawne used that device to swap bodies it allowed his body/dna to be a conduit so when all the wells were brought back to life so was thawne.
the AI speedforce was shutdown, my guess when barry threw lightning at it to destroy it that he must of had some residual speedforce left to allow him to do that.
However, I'm sure everyone noticed that shortly after barry's lightning was blue, and I don't think he was extracting velocity x from frost because like he said during there battle that the velocity x was pretty much out of her system which meant no more speed so there wouldn't be speed or blue lighting being sucked out of frost and transferred to barry.
my guess, possibly when his mind was working a super speed it subconsciously made him generate the speed force like he does in the comics which is why his lightning was blue because there's no reason why that should have happened, it wasn't like barry injected himself with velocity x.
this is actually a good way of explaining this if the writers are going that direction.....this would put a rest to the AI speed force which i did not really like and still hoping that's not the permanent speed force.
This would also explain why thawne could be back....now that barry has tapped into the ability to generate the speed force, he is the engine and without him nobody has speed but all of a sudden we see clips of thawne and reverse flash....barry obviously plays the biggest role in all speedsters lives, basically they all need him or they have no speed, and i'm sure reverse flash knew all this was going to happen which is why he seems to never die for good, he's always a step ahead.
remember when he came out of the speed force he was talking all wierd, writing down those symbols, and then he went and saved iris from samuroid and cysco said he's never seen barry run that fast, actually he says no speedster has gone that fast....maybe it's like he was able to tap into more of his abilities, I think his brain being at super speed COULD have allowed him to tap into the ability to re-generate the speed force and therefore be the engine for him and all others without really knowing that it happened.