Cool stuff, the effects are organic and blend well with each other. I will say, though, that the trailer is extremely ambiguous... without the title of the game at the end I would have absolutely no idea what I was watching. So while one of my critiques was a lack of identity for the sound design, I realize that much of that is due to what's missing in the trailer itself.
The action in the trailer is very up-close and in-your-face, and I think the effects you've designed would be better served without so much reverb. For this one I would think of reverb as a little mortar between the bricks, and allow only certain sounds to excite a reverb. The gunshots, for instance, sound very washed out and have little impact. Perhaps try varying the use of reverb with the use of delay. Delay can be a great way to add space without feeling like the sound is "back in a room".
The whole idea of 'size' in sound comes in a few dimensions: volume, width of frequency range, use of stereo/surround field, and number of reflections (delay and reverb), to name a few. An increase in any, or all, of the above will result in a feeling of larger size to your effects. You can't rely just on volume if you don't know what people are listening on, so when a sound is meant to sound 'larger' try filling out the frequency spectrum, spread it over the stereo field, and allow that sound to excite a space created from delay/reverb.
Cool stuff, good luck!