It's not impenetrable? It's just fortified and hidden. If you find it then it will just need time to get in.
Supplies is perfectly reasonable, water is easy to find and food is simple to grow underground with the right lights.
High tech weaponry thats highly limited and only a prototype to use against an enemy that outnumbers me hundreds of thousands to one.
Hardly a game breaker.
How exactly is 90 vehicles larger then a small country?
You're missing the point, but I'll counter your points one by one:
1. It's still better than everyone else's bases.
2. Do you understand how that makes you immune to sieges? (Assuming that you somehow have sufficient fertilizer and power.)
3. True, but A. they're not all or even many going to attack you at once and B.
where did you get it?4. 90 vehicles including helicopters and such is better than many small countries have. The most important word is
small. Still, you're a lot smaller than almost
any country. Why and how do you have so many vehicles?
5. Overall? No one thing is game-breaking, but altogether you have a Jack and Near-Master of All Trades with
no weaknesses short of a good-sized nuke (which darn near
everything is weak to), which is, in fact, the rough equivalent of 3.5's Druid class. If it leveled up at twice the speed everyone else did.
But I'll edit it a little bit, hardly unfair considering it's 4000 ish against hundreds of millions and some dragons can do the same by breathing.
Are you familiar with guerrilla warfare? Then get read up on it.
If you're considering who would win in open war, you're doing it wrong.