I love it! I have personally been looking for some kind of magfed pump lately to break into. I really like the idea behind the pumps over at ADN using autococker components but what is holding me back is what kind of magazine I'd like to see used. Using the nelson valve design is a good idea though because of the simplicity behind it. As for what you mentioned above, these are my thoughts:
-Dye DAM mags
-ASA at the bottom of the grip
-Yes on the Gargoyle features (based on what you have listed, I have limited knowledge on the platform)
-No hopper integration
I personally like CA over 12 grams but if it would be possible, the ability to use both in some way would be neat. Autococker threading would open up a lot more options for barrel choices, especially when looking at rifled barrels for shooting first strikes. As for mag, the DAM mags seemed to function well at a good price point. I always found that air run through the bottom of the grip was the most comfortable to play with too.
Good luck with your idea though! I am excited to see where this goes!