Is it Constitutional?

No. Can it become constitutional? yes.

Think of what Trump said about the Republic ......Listen carefully.

Is it a pyramid scheme

Yes. But everything is. It is called supply and demand.

to enslave those who don't have the knowledge of it?

No. If you have no knowledge, it is better to stay off. That said, obtaining knowledge is a matter of effort and desire. It is your choice to know.

Start small. Test it.

Is it safe? What does it depend upon?

On energy for sure. Then also Internet access, and .....

1. adoption by more people
2. meddling free

But remember: it is an asset. Not a payment system anymore. If you want to pay something, use Bitcoin cash (BCH). You can be up and running within 5 minutes. And ready to receive payments within a second against a 10th of a cent. If you want to be secure and anonymous: use Monero.

Safety depends on your threat model, and frankly, on your own behavior.