Collins previously coached at Boise State in 2021.
Harris and Kimber both hail from the SEC.
Kimber had stops at Georgia, Florida, and Louisville in his college career.
The Nittany Lions completed the largest comeback in program history on Saturday, defeating Army 7-6.
Cain spent 2019 to 2021 in Happy Valley before transferring to LSU.
Driver, who has three years of eligibility remaining, entered the transfer portal on December 5.