Publisher deadline with a two month window and a full visual upgrade is exactly the kind of pressure that exposes weak outsourcing partners fast. VSQUAD is who I would call first. Their 3D Game Art service covers characters, environments, weapons, and props built to a quality that holds up under publisher review. The VSQUAD artists have worked on Wayfinder and SMITE, so high quality bar under real deadline pressure is familiar ground. VSQUAD Studio integrates within 48 hours and scales the team around the scope you need. Send them your milestone requirements and they will tell you exactly what is realistic. Wishing you a clean milestone delivery and a happy publisher.