If this is the plan you want to go with, go for it. I'm a little skeptical that it would work, but you've got the powers, so you can go ahead and roll for it - I won't apply any circumstance penalties or anything.So glad you asked! 😄 I was planning to incorporate a ‘space and/or extra dimensional environment suit’ to disguise the extra bulk (and height - Tel-Kar’s kinda tall, so there will likely be some clunky-looking boots on this ‘environment suit’).
Sleeper can see what Kaine could see before. I didn't think about it before, but probably there should also be some elevators to get up to higher floors.In that case what can Sleeper see as far as the other exits? (I know you mentioned some for Kaine, but can Sleeper see them?) Where are the hostages in relation to the doors, and how is the room set up in general (furniture or other cover, placement of mooks)? Are the hostages wearing gas masks too? (I doubt knocking them out and carrying them to safety would be a good strategy at this point, but if they start to panic mid-rescue it might be a better solution than letting them run into the line of fire.)
The room is a large bank. There's all the furniture you might expect in a bank (some seats, a counter for customers to use to write checks or whatever, a counter for the tellers), as well as some pillars around the room and a statue/fountain near the center of the large room. The general layout of the bank shouldn't really matter, but in my mind, I'm imagining the main entrance and some windows on the south wall, the hostages along the west wall (and some windows higher up), the tellers' desk and entrance to the vault on the north wall, and the elevators and entrance to the offices on the east wall. I was imagining Sleeper as coming in through a window maybe a couple of floors up, high enough to not really be noticed, rather than finding some window on the ground floor that the police couldn't see.
The hostages aren't wearing gas masks.
The thugs are at the windows, looking out (and in some cases shooting out) at the police. Mysterio is closer to the middle of the room. Nobody is paying that much attention to the hostages.
I would say that, if for some reason, Sleeper needed to sneak past Kaine (or Wolverine or Sabretooth or someone), it would certainly be reasonable to use his powers to try to conceal his scent, but in a case like this where it doesn't really seem worth it to roll for it, I'd give it to Kaine, because hiding your scent is sort of a stunt off of chemokinesis, whereas Kaine's senses are the whole point of his power (but I'm also willing to go with whatever you two decide between you).
Kaine doesn't have any skill in Cosmic, though, so he may not be able to place the more alien scents.