Now I am recording a series of gameplay on 6/6 Fallen Spire, first time encounter so no spoil!!
The exogalactic and CPAs get so powerful that, well, Mini fortress are basically... Cannon fodders, and it does not survive long enough to repair anything (probably because I place them right on the enemies' track).
On the other hand, since I need to fortify the damn chokepoints, I unlocked ALL Fortresses except the modular one. FIVE of them (plus two minies) are placed on my entry choke point, THREE on each exit branch worlds. None of them are in line of enemy movement. The result: the entry choke point Fortress Cluster kills like 1/3 of the Exo waves, but unfortunately the lower marks die to CPAs(because Exos simply ignore my defence there). None of the fortresses are in the way of the enemy, so they don't die.
BTW, pretty interesting to see five fortresses repairing each other. But any major repairs still need my Combat Engineering Team (40 MkIII Engrs!!!) or my Galaxy Express Engineereing Team (I call it GalEx) (7 MkIII, 1 Mobile Builders, 2 Remains Rebuilders, stuffed in a MkII Jumpship).
I am currently stuck a bit since, to my surprise, I need a whole lot of K after construction of Galactic Capitol... I was never told to do so, so well, what a surprise! I have 0 K left!
Worse, as I mentioned in another thread, my choke point is right next to a Core World. So that is also their choke point. At closing to 400 AIP, I need some serious planning to establish on the other side of the galaxy, raid for its K (and asteroids, I located three Titanites! I want Mark V Jumpships!), and abandon.
So K thirsty that I actually K hacked on that Core World. Not much response, though. I have so much HaP that I just popped a Hacking device on the edge of CW and left it there until K's are all extracted, and moved the hacker back(Of course, I used Mini-Rams to take down the Tachyon emitter of the entry point, which provoked a HUGE special force. I waited for them to settle down).
I am even considering kill the first AI Homeworld before advancing the Fallen Spire campaign because the Exos are coming so quickly when it is two hops away.
I heard that AIP will bump up 100 though, so still resistant to do so since currently I am not doing too well in defending those combined Exo+CPA+Threat waves.