If I don't focus 100% of my energy on trying to complete all 10 of the zolazin missions (completed 1 now), I won't be able to finish them all in time (might still fall short anyway, but no big). So what I want to know is: is there a limit to how many shroud bases I can have in my battle screen? probably wouldn't make sense to go for 100% completion if the enemies themselves won't all be there waiting for me to get around to killing them

Well when fighting the stryll tracker it added an extra space, so I think youll be able to see all ten.

I had five NPC's on my screen earlier - Shroud Base plus the standard 4. While I was on the screen, one of the standard NPC's expired. The number of NPC's then dropped to 4 when I reloaded; the fourth standard NPC did not regenerate as normal, so i'm assuming the game counts the Shroud Base as the fourth NPC. I'm therefore not sure if it will work as you expect.

whew, finally got rid of all the shroud bases I accumulated from that mission. now I can go on to slaughter other things

Ya you can have as many as you want as long as your missions keep giving them to you. However once your normal four go away they do not come back till you have an extra spot open for them.