>> The whole game balance has to be revised
I don't think anyone would disagree with that, but there's little point trying to balance a game which still has major gameplay elements missing. Introducing psionics will no doubt radically change the balance, as will a true visibility system, and any changes to the PHALANX equipment lists, and so on.
If the introduction of some element totally breaks the game, and makes it unplayable, then that would need attention, presumably, but other than that, trying to balance an unfinished game is a diversion of effort from actually implenting new content.
>> TOO MANY UFOS ARE SPAWNED
Then again, you can equally argue that the UFO appearances are what fund PHALANX expansion (in my current game, expenses outstrip funding by a considerable margin, so I depend on alien tech sales not just for keeping what I have going, but for any future expansion. I still need at least 2 more bases).
I know what you mean though, it can be frustrating watching the research figures creeping up so slowly because of the frequency of missions and the need to handle them manually. I think it's likely that research will be one of the areas that gets a lot of attention during balancing though, because it is so critical to the development of the gameplay.
The rate of UFO appearance is also clearly a critcal part, but if it was turned down too low it could also be a problem, due to loss of funds from tech sales, less experienced soldiers and less loot generally. Until the game is more complete, it is impossible to say what the "right" level of UFO activity might be, and personally, I'd rather the dev effort went on adding shiny new toy than crippling my economy