Don't worry, I haven't completely lost my mind here.
I selected the Aliens setting because of the following:
1. Colonial Marines . . . automatic plothook.
2. They have synthetics (I prefer artificial person, myself) . . . so the 13th Colony has their own Cylons or do they?
3. The technology level is generally the same. Big difference? Sulaco covers 0.74 light-years per day, while the Colonies have their instant-jump fold-space drive. Both have anti-gravity, both rely PRIMARILY on kinetic weapons and missiles and nukes. BUT, the Earth of this setting ALSO has directed energy weapons (but no shields) which should come as a MAJOR SUPRISE to the Cylons.
That was the big three reasons. And LV-426 is just 39 light years from EARTH. Now think about this. This is the Earth of 2179, just a few centuries from now. Earth with BILLIONS of people and major colonies. All ripe for attack by the Cylons.
Can this be interesting? I hope so. Anyway, it isn't nearly as much of a curb-stomp Cross-over as a lot of people like on this site. I mean mixing Star Trek and BSG, or Star Wars and BSG, or 40K and BSG, the power levels are just so dramatically different.
Here, not so much. And that gives me (and you the reader) a chance to focus on the story and not on the huge gaping holes in plot because of the technological disparity.
Now, I am not using the far-left field A vs. P stuff, or integratng the Predators, or having the Aliens change their own DNA with each host (silly idea) and I think you might like where this goes.
Anyway, that is my thoughts. I hope that you guys continue to read and offer me your opinions.