Hmm ....
I'd love to help, but I think a lot of it for me is how it feels, which is hard to say without having experienced it yet. I guess I just reacted to the fact that the large ship missions would be "easier" because you didn't have to deal with Psi attacks much. I've played a few months game time but haven't gotten to anything big enough to experience how it currently is. Just did a cargo ship terror mission with Tasoth and didn't experience any psi attacks at all.
I'm definitely of the opinion that XCom shouldn't be able to do Psi attacks without LOS. So, maybe it's fine the way it is. But, I also don't want to completely nerf that element of the game, because I recall alien psi attacks that could hit you anywhere be very tense and unnerving. Fair? Probably not, but ...
Perhaps playing with some numbers would be helpful? Maybe it wouldn't be so bad if the aliens could still do the original types of attacks but maybe not quite so annoying. In that case, would it be possible to turn on LOS requirements for just XCom? Probably not, but seems like a good solution to me. I think the problem is, in the vanilla game, while the alien psi attacks were a pain, in the hands of XCom, it would just completely break the game. Sure, I don't have to do that, but .... the spirit is sometimes weak.
Sorry, don't have any definite concrete suggestions. I'll keep playing and post any further thoughts I might have. I'm not sure I understand having psi "ammo" would work.
On another topic ...
While I'm thinking about it, what are the chances of getting better USOpedia entries for the laser weapons? It is SO NICE to have those for the land battles (frankly, they're probably the only reason I survived that first cargo ship terror mission), but now that I've started getting Gauss and Sonic weapons, I find I have no way to compare which weapons are more effective other than observing the TU costs. I've only got Gauss/sonic pistols at the moment, and I can see how the sonic hits harder but are not as fast. How does the laser pistol compare? I can't tell ingame. Just a thought.
Really enjoying the mod so far. I'm only on Experienced and that may be slightly easy for me, but I enjoy not getting crushed constantly.
Thanks for sharing.