I have not seen Firestar or Mercury in years. Did they ever make any appearances during the T-Mists thing?
As for Laura being on a team. I'm not too sure. I think it would be great but I fear that writers wouldn't get how to do her character and just make her a female wolverine. Or that atrocious characterization they did with her in All New X-men when she was going "brb" and "I'm mother f***ing Wolverine!".