Also, the gear she's wearing in the final lot of scans looks really really nice and it saddens me they stuck her back in the star spangled knickers when this would have made a perfecr transition point to a new costume.
And another thing that I notice is related to WML's woeful inability to comprehend numbers -- hundreds of womenplanets</i>?? The initial set up of the Krell with the change every century makes a sort of sense if you squint and think he's trying to homage Left Hand of Darkness and mayhaps the classic Doctor Who story "The Mutants"; the assumption of the multiple century lifespan this would require is something of a science fantasy staple and there are many examples of life here on Earth that demonstrate similarly stupidly vulnerable breeding behaviour. The outlier appearance of individuals of opposing gender to the majority that's referenced later makes sense from an evolutionary standpoint as essentially a form of insurance against catastrophic failure of the primary breeding cycle.
That cycle itself is interesting. It comes around every century, but obviously has to take course over a period of at least a few years. Is the basis for who changes first based on genetic lottery or simply age? Is there a period of functional hermaphrodism or is the change much more drastic? Do you spend equal cycles male and female, or do you flip sufficiently often to die as you were born?
The inexplicable increase of the period between gender shift by an order of magnitude seems to imply not only amor econventional life span but that either the males get pregnant (which as the capacity for pregnancy is surely what biologically makes a female a female you're looking at the terms male and female as nothing but personality descriptors) or that the species spends its male phase impregnating all manner of female aliens and thus its female phase being impregnated by alien men, which starts towards the Mars Needs Women trope of aliens whose DNA utterly overwhelms that of the host partner.
Trying fannishly to make it all fit together, from that latter point of view in the paragraph above you could see the current krell attutude towards women developing -- let's assume that they develop spaceflight towars the end of a male cycle, flip over as per usual, expand peacefully enough during the female cycle and discover that they can interbreed with aliens, then flip back to being male. At this point the guys have been handed a flourishing domain along with the discovery that they no longer require female krell in order to continue the race. No krell ever has to get pregnant again because the rest of the galaxy can be their brood mares, and if that's the case, then in theory the krell need never undergo another gender flip and whatever the hell physical effects that have tp be endured because of it.
So suddenly, the rest fo the galaxy finds itself caught unawares as this peaceful feminine society wigs out and starts conquoring places. And while their scientists may have cracked how to hold off the vast majority of the krell from undergoing their regular gendershift, either they can't quite handle unchaining the procreative urge conversely maybe chaining it is the payoff for halting the change. So all these prison planets that have been set up quite likely become rape camps every, oh, seven years or so, and Diana and Natasha were just really lucky to have encountered these guys during a lull.