Well one way could be to increase the time for railgun to finish.
But actually I think plasma tech isn't that useful anyway...
I however completely disagree on this:
"Remove some starting equipment, especially combat armor."
No, thank you. Just because for balance reason? How silly is it
to move against very dangerous aliens without armour? Come on ...
noone would do that. If you want to balance the research project,
then find other ways.
"Remove the alien armor from the beginning of the game"
Guess you suggest this only because alien armour will become
useful. (Or in general, all alien tech.)
A suggestion is to simply make researching alien stuff
harder/more expensive/more time consuming.
"Put some tech before the railgun. "
Agreed. Though, you didnt specify what exactly to put before.
"Improve the laser (kind of replacement for the rail gun) and make it a little less powerful "
I think this is a bad suggestion. The way lies to make rail gun harder to get, rather
than making laser a replacement for the rail gun.
"Right now, if a UFO is detected, there is almost no chance to get it (had about 10 UFO sightings, lauched fighters and lost contact...boring)."
Depends on the bases and interceptors. If one has enough bases with several interceptors from different directions, it is
normally very easy to intercept an UFO.
On the hard levels though, I do indeed have cash problems
"Add some special ammo (e.g. armor piercing)."
Totally agreed on that, for several reasons.
What I think could happen would be that the alien tech gets a slight boost, the research cost is increased too,
and maybe the initial requirements for "decoding" alien tech could be made a bit harder as well.