This is a Republic Side Mod which converts the Republic side from the default 501st troopers to Galactic Marines.
Screenshots of version 1.3.1, which has Bacara replacing Mundi, rather than as an extra unit (as in 1.3.0). Bacara also has his own custom rifle which is rather good, yet he can still be easily killed and runs out of ammo fairly quickly, so you must still watch out!
Version 1.3.1 Download available on the download tab, enjoy.