Hmm idk?.. A frozen predark special forces team, equipped with all the fixens accidentally thawed by a CPU malfunction in some long forgotten redoubt, commander still thinks America is at war, may even have access to mini nukes, or locations to unused nuke stock piles. Has intimate knowledge and free passage through the redoubts.
Add a supernatural element, hell it's already been proven that damn near anything can happen in the James Axler universe, some lone white coat like j'aimevous experimenting with forces far beyond time travel opens gateway to lost realm/dimension unleashes forces or creatures beyond his reasoning ala Stephen kings the mist,( US mil experimenting with gateway technology)
Bio weapon storage units on mars or the moon, ultra secret base, with accidental jump to these places, meet highly intelligent bio weapon who has been plotting invasion, kind of like kaa and the mutants except ultra psychotic and evil. A DOOM like scenario.
To play on the supernatural a little more, possession of humans by said creatures or forces as mentioned above. add more of a truly brutal or undead feel, that makes the companions truly question themselves and their beliefs of the intangible Ryan in particular.( something that could bring the true apocalypse in biblical sense) Something so terrifying to see that even mutants like flame crazed stickies would turn tail and run at first sight.
A master white coat from another casement who has perfected interspacial placement, individual attempts to merge his dimension with deathlands. Also more threats from other casements, see how their armies, tech and ways of thinking stack up against the companions.
More on Melphi and Kelphi cyborgs.
Companions make cron jump manage to thwart sky dark, but realize when they jump back home nothing has changed because each timeline is locked into its own linear path. Well atleast they saved another casement.
Operation chronos trawls Ryan back by accident after hunting for doc in the deathlands, doc gets pushed out of the way of the portal by Ryan and gets sucked in.
Companions find the true origin of jak, maybe he really is a bio weapon, foster parents found him at an early age ( could have came out of cryo storage by accident) alone in the swamp or woods as a small child. This might make a good origin story. Either way it shouldn't change the way the companions feel about him. (Maybe was part of a forgotten super soldier program)
The companions learn about the archons or bits and pieces of them.
Fight with ET a predator esque hunt type of deal, would be nice to see how they'd do against a totally non human origin threat, with an epic bloody hand to hand fight between Ryan and one of the alien hunters. Like Arnold and the pred. Hmmm maybe even kristi by some way able to lend Ryan her Gaia abilities for the task.
Ryan makes an appearance in outlanders......
Forgive me for reaching, these are just some of the many ideas I have dreamed up.