Psi has long been an issue and your desire to remove it from the player is essentially rediscovering Xenonauts.
Players weren't too happy about that, either. Nor the removal of Blaster Bombs.
Yankes has already listed a lot of common counters to psionics, although he missed what's probably the most important of them all: disallowing psi-waves propagating through the ether or, in plain language, making the power of psi attacks scale (edit: more strongly) with range.
Another thing along the lines of only allowing panic at first is to give the psions an actual damaging attack. I did that years ago with the goal of removing the 'psi lightning rod' tactic, by making both player and alien psi have a stun attack. I think already Apocalypse had psi-stunning? Anyway, that solved the issue of the 'lightning rod' who went to sleep and ceased to be a problem without removing all agency from the player - the victim is still alive and can even be revived if need be.
Otherwise, I watched the original stream from Trauson and caught some of yesterday's stream. I think I saw the Tasoth-napping and the first batch of Lobstermen.
In any case, the strongest impression I got from his play was that vanilla grenade range is utterly broken, as I've been preaching on occasion. I'm using instant grenades myself, instant (heh) gratification whore that I am, but I also restrict throwing ranges to 12 tiles (and Trauson made me think even that is too much) and make them explode in inventory when time is up. This means no pre-priming shenanigans, no man-mortars, and grenade relays have to use inert grenades and thus the point man or woman must be able to prime as well as throw.
The second was just how much he abused his invulnerable cover. The missile spam during the base attack only failed because TFTD elevetors are made of indesctructible hard light. Not to mention all the abuse heaped on the Triton.
Third, I think there's some danger in refining the AI exclusively with OG and TFTD playthroughs. Both of the original games had a lot of shortcomings that have seen various tweaks and additions over the course of the OXC and OXCE projects. And they're pretty barebones compared to many mod offerings available here and elsewhere.
As to the reverse difficulty curve, I'm personally not against it. Playing a game that gets harder and harder and then ball-crushingly hard is an exercise in masochism.
Although the degree (or maybe slope) of this curve with BAI is certainly something.
Otherwise, the original "aliens prime all their grenades and blow up all the loot" idea was pure evil.
And alien sniping and cover use is really what I like to see from them. Blowing up the landscape, themselves and precious veteran soldiers with Pulsers and PWTs, not so much.