A trilogy, perhaps?

this might be too overambitious at this stage, but it might be worth concidering.

say there was to be a trilogy.
the first part could be the nazi ww2 operation, the second one the soviets or the us during the cold war (probably the soviets concidering the brainstorming idea regarding documented mail exchange between DDR and the USSR about what the nazis tried to find, great idea!), and the third one set in a future where europe has lost its powerful position.

to link them all together, we must introduce a lure other than the aryan origins at least as soon as in the second part. Such as a powerful tool/weapon/wealthbringer. I'm thinking that if some parts of my idea written below is going to be used, the treasure later search teams are after are the forbidden fruits of the tree in eden (that just brings destruction and torment, really, but noone will realize that).

A nice roundup of my previous idea would be that there's just one or a few survinging the ordeal, and that they manage, at last, to dispatch a message to the outside world: "We've found the forbidden fruit." Then the leaders of the third reich would know at least something about the first missing u-boot. which the soviets would look after. and then the students which Gert-Jan mentioned in his idea.

In all three parts, a mighty empire is desperate for more power (be it propaganda value (first film) or a turning point in war (second film) or in economic competition (third one)), and in the end, the individual has to suffer.

The good thing with this trilogy-setup is that the first film will need least resources. a bunch of actors, some props, a pair of blue blankets, 3d-rendering for the boot's interior/exterior, and a bunch of scenes in atlantis. I'm sure a soviet adventur would generate more 3d-rendering work. The same for if the storyline is that they're building a new boot from old blueprints. In other words, the project could grow part by part of the trilogy.

EDIT:
It could also be three movies put in another way one fore atlantis and one for hyperborea where atlantis focuses on discoveries with references from the bible (exile from eden, tower of babel, noah's ark), Hyperborea whith references from norse mythology (such as raganrök, fenriswolf etc), india and tibet (references from hindu writings such as kali yuga -the darkest of all ages - shiva, the swastika's origins etc etc) - all three has played an important role for the myths that inspired the whole mindset of the third reich and also later neonazi movements. Just an interesting thought, i think.