Rather than simply listing over a dozen planets which I'd like to see added into the mod, I'll post a couple with detailed reasons why they're relevant during this era (New Republic era 5 ABY - 25 ABY). First I'll post three and then hopefully wait for any feedback from the devs whether they'd be considered to be added in. My first three planet suggestions are:
Ithor
The fourth planet in the Ottega system (also known as the Ithori system), within the Mid Rim. Ithor was the home planet of the Ithorians which considered the planet sacred, to which they built floating cities so not to harm the surface which housed rainforests and many fauna and flora such as the Bafforr tree, crystalline trees with collective sentient consciousness.
After the battle of Generis which saw a victory for the Empire, Thrawn then lead his forces to Fedje, Ketaris, Agamar and then finally Ithor as part of his main campaign against the New Republic. Ithor was a member of the New Republic and was even a New Republic stronghold until Thrawn had annexed the system. Known as the "Third Battle of Ithor", it was one of Thrawn's last conquests before his defeat at Bilbringi.
Naboo
According to Star Wars: The Essential Atlas, Naboo was a member of the New Republic and during Zsinj's conquests and Thrawn's campaign, it was the location of a New Republic stronghold.
Fest
The primary planet of the Fest system, located within the Outer Rim Territories, a densely populated ice planet with various mountains and valleys. The planet was controlled by the Galactic Empire and was the site of an Imperial weapons research facility.
During Thrawn's campaign, the planet was under the control of the Pentastar Alignment. However when Ardus Kaine was killed during Operation Shadow Hand, Fest along with the worlds controlled by the Alignment were gained back by the Imperial Remnant under Gilad Pellaeon's rule a year later after Kaine's death.