Brice and Evans might just make Janis expendable as far as coverage units go. Both seem to be strong tacklers and cover a lot of ground.
Hawkins has been decent as a corner but he's not shown up at all on ST. They've used him as a gunner at times and he's been completely dominated. He could be a keeper for the roster eventually but not this year. He'll need to make it to the PS and get himself ready to take another shot next year IMO. If somebody wants to take a shot on him and claim him then I'd wish him and them the best of luck with that. If they have any intent on him playing special teams that isn't likely to happen.
I think Burks brings more than Crockett too - other than a year's worth of experience which is worth something but not much at the 3rd RB in my opinion.
I too love Callahan, but also think it's worth the risk to cut him and bring him back on the PS. I'm not sure GM's take shots with undersized over-achieving undrafted rookies. It's usually the underachievers with all the measurables, physical tools and big upside potential GM's like to grab.