Historically, plaxes that seccede typically will sieze (or try to) all military equipment within their declared borders. This would include both Federal and CNG equipment. It will be a Scherpunkt to hinge the success of their seccession.
On that topic, they'd have a significant political problem in all of the Marine & USN forces available in SoCal around San Diego. Forces whose bosses are very likely to tell them to return CA to the Union, and give back all the USG stuff in their possesion. There would be a significant problem in NoCal of the locals likely welcoming Federal forces from OR, ID, and NV to through off the yoke of percieved oppression from Sacramento. Note that this presumes that military forces within CA would be willing to turn arms against US forces (the tape on the pocket of California National Guard units reads "US Armry") at the will of the political masters of California. And, Federal resistance is going to be right away. Well before foriegn actors could deliver materiel. So, the putative CA forces would need some sort of color/shape blazon to identify their equipment.
Those are concerns with the narrative as background, which is more dramatis rationare.
The practical aspects for modeling a dio are a bit more concrete. The modern battlefied is a very empty place. MLR (Main Line of Resistance) can be 5km deep. Which is close to 70m in 1/72, so foreshortening is going to be required. 300m worth of rifle shot is 4m at 1/72--so again, foreshortening is needed.
You'd have to be careful with using terrain features to foreshorten the MLR. CA is unlikely to have air superiority, which means not only will terrain be vulnerable to defilade artillery fires, but also close air support.
So, the answer is probably to show only one side of the conflict at a time. The CA side will need a terrain feature, like a ditch or canyon, or, perhaps a railway embankment. With overhead cover, probably enhanced with camo netting. The CA forces will need some sort of distinctive marking, like armbands, and or head gear; the vehicles some sort of flash or blazon.
The federal side would like use a similar featrue to anchor their side of the line. But, they will need nearly no overhead cover. If a FOB, there will be arty, like as not. They will have a lot of supplies, too, from having far superior (quantity if not quality) trains units on their side. FOB will likely have a drone launch & recovery point.
So, it's do-able. Might wind up as a series of vignettes.
If you could find some 1/72 CHP vehicles you could do the gate of the NTC, as that institution is unlikely to meekly join CA just because they were told to. Especially with a unit coming off a training rotation, so they would be very salty. And, the OppFor at NTC would allow for some facinating vehicles to guard the gate, like a Zilka and the like.
Or, for that matter the Port Hueneme reservation, HQ of the SeaBEEs.