I think this would work nice as a seperate game mode. Either that or, if a base grows too large, that is when it will show up for enemies.

If you can have bases that are hidden when created, and they eventually become fully established with depots and plenty of supplies, it's now an important objective that you can't do anything about until you come across it. Which I get is the point of your idea, but this might not be good if people develop strategies around building as many undetected bases as possible.

Since bases right now always show up when they have radio connection, it means that you, as a player, have to be careful about where/when you are building a base. Somone sees a new icon on the map, and they can immediately spring into action to stop you from building a new base.

But if bases are hidden at first, anyone can essentially build lines of bases closer and closer to enemy objectives so that all you have to do is spawn, walk 100-200 meters, overwhelm anyone there, and cap the objective. And if you die, respawning and getting back to where you were becomes super easy.

I could also see it working nicely where each team is allowed to only have 1 "hidden base", and that base is different in that you can only build small vehicle depots, 1 Ai barrack, and maybe a few other small things. And so you'd have to strategize with where you want to establish this base, but if you manage to do it, it would grant your team the ability to infiltrate deep into the enemies territory and either cap some points, or divert some of their solders from the front line so it's easier to push in other places.

But like I said in the beginning, I also like the idea of a game mode that's based on the idea of finding hidden bases. The game would start by each team picking a "commander", and the commander would pick 3 to 5 locations where hidden bases will be built. The map would be pre-divided between BLUFOR and OPFOR, so that you can't accidently place your base in the same spot as the enemy. Once each commander has picked their spots. People will be able to spawn at one of their spots (from a command tent), and they will have to build up their base as usual. The goal is to find and blow up all of the enemie's bases by destroying their command tents (or something like that). Blowing up a command tent results in no longer being able to spawn there. Which means you now have fewer places to spawn from; more likely to be overwhelmed by spawn campers.