The lack of Ion Cannon attacks is due to, if I'm not mistaken, the fact that you took out satelllite support on the previous mission.
Also, the fact that Midian prefers ballistic instead of plasma weaponry is justified by the fact that the "tech tree" gives the player, in the campaign, long-range weapons first, which is then compensated later, as if each race had taken different developmental or evolutionary paths.
This mission was very difficult for me, and had to recur to drastic measures.
Your commentary about the lack of Ion strikes on the surface of Midian reminds me of this:
Ever since I made this thread I have a "Machines" folder on my desktop to remind me that I should give this texture upscaling another shot. Few weeks ago I even managed to install ESRGAN like M123 suggested. I used this tutorial to install it properly, if anyone is interested:
Now I finally gave up on this idea, I think it is not worth it at current state. 256x256 is very limiting to make much of a difference and let's be honest, there is too much work and who would even care in the end.
I asked the maker of dgVoodoo about the possibility of injecting higher resolution textures using his wrapper and he said it might be possible some day in the future, so maybe then it would make more sense to work on this...