Uhmm... some questions and answers:
Q: "Are these going to only be for JA, or are they JO compatible, too?"
A: The model is a part of the mod and its going to be JA only. Recoding it all for JO would be a pain and there's no vehicles in JO :\
Q: "Should have asked this earlier but, is this a SP mod or MP ?"
A: For now its just MP. If we have the time we will put some SP missions, but for now, MP is what we want to change. I can assure you that if we do SP, its not gonna be one of those cheap 'replace the player models, but it still follows the orignal game's story' mods. We will use the player models and levels to make a new SP story.
And about the bulltet time, its going to be a pickup that you can chose when to use and it enables bullet time for about 5 seconds or so. If you have played the specialists mod for half-life, you will see this works quite well.