It isn't in the game as of today, but a dataminer has found evidence that a character customisation system for Star Wars: Battlefront 2 is probably on the way.
uninspired_zebra - who has also found a bunch of other stuff digging through the game's code - recorded video of the menu in action, showing how you're able to apply a bunch of skins to soldiers.
Only Clone Troopers were available to browse through (other factions "just take you to a blank screen") in the video above, but uninspired_zebra was later able to find examples from some other units as well:
If I can get my boys looking like this, that would be nice.
Other stuff uninspired_zebra has been able to find include previously-announced pieces of DLC (such as Captain Phasma), making it likely that this menu will be introduced as part of a future update to the game.