It is suicidal to camp an open-ramp ship, as you were trying to do.
It was Star Gods Terror Ship on desert map. I tried several times, reloading to turn 1, but in open terrain, with only custom power armor and 2 tanks, but without shields or assasin armor spotters it was slaughter every single time. Simply not possible at my current tech level. And I defeated them during Mutant Pogrom in urban area using Turtle and no tanks, and only thing that threatened my victory was destruction of rear door. To stand in open outside the craft and survive against Star Gods I need better gear, but with me getting better gear they will loose part of their superiority and will be less dangerous enemy. And if I defeat them in open battle with better gear, my success will be attributed to that gear, not the ship I disembark from.
Different codexes have no bearing on the late mid-end game open ramp ships. Once you get past early game, almost all of the larger assault craft are open ramp concept. A different codex might give you tools to be more aggressive, but often those tools are late to end game.
I was thinking about stuff from Red Codex regarding tactical combat.
Regarding the summoning circle, you might as well keep it, it only spawns a single 1x1 unit, usually just a low rank one. Considering you start with someone in the room with them, its usually just a matter of walk a few steps and apply melee.
I am pretty sure that at least 2 enemy units spawned there, but not 100% sure. The bad thing is all hands in that base were recruits, who saw combat only once. They had impressive period of training in dojos, but training doesn't improve reactions, so their initiative was rather bad. And they even wasn't armed for melee. Good thing is I was playing in "spectator" mode, checking if Reticulans already left bars on Alpha Centauri and reached Earth. Attack occured only because I ignored enemy ship that was searching for my bases.
EDIT:
I decided that SC will stay, since it is research base, but lesson is learned and I will rebuild Hyperwave Decoder there to minimalize possibility of detection and attack.