you know, part of me kind of thought you could use elements from Gundam Unicorn, giving the model number RX-0, or even the RX-Zeromaru real type form from Gundam Build Divers; since the SD head attaches to the back and look like a humpback like how the knightmare frames from Code Geass are like.

Gundam oo raiser pls.

I prefer number one.

I would prefer you to focus on one story then after you finish do the other. at very least you won't be confused and mix up the stories. I think you should call lelouch's Geass something along the lines of absolute awakening or absolute limiter break. another title for 00 could be the 2 zeros of revolution or maybe lelouch the innovator.

Intriguing prologue that can either lead to two stories.

this was underwhelming

Off to a good start so far. I think you'll do a fine job with this crossover, but personally I would go the route of 2b. That way, you'll preserve your ideas better. Also, other than Lelouch/Kallen, any idea on some of the other pairings and/or inclusion of some of the side materials (Akito the Exiled/Oz the Reflection/Lost Colors)?