it will be backed by tangible assets
There's already Xaurum, backed by gold and even with some deflationary rules in it, to make it attractive as investment.
For now your idea doesn't seem to bring something really new and useful, but maybe you explained too short to avoid people stealing your idea.
Because of these unique characteristics, all coins have to be issued (or premined) at the beginning
...
I have thought that maybe it could be implemented with a POS system, or even develop the cryptocurrency in some established platform.
For a project with these characteristics, which system would be the best?
If your coins are premined, you don't really need Pow nor PoS, you don't want to distribute more coins than you've premined and sold... I guess...
And then a token already does the job, whether it's on Ethereum, Waves or other ecosystems. Just be warned, if you make such token, the network fees may have to be paid in the network's coin.
Or, if you want to avoid this, you'll need indeed a coin. You can make it centralized or you can give some small rewards to people to keep nodes and make your network decentralized. Then PoS or LPoS (see WAVES) can be an idea. I think, however, that whatever you do, at start the system will have to be quite centralized (you own most nodes) if you go on the coin direction.
I guess that you can try to find/read how Xaurum works and how Waves nodes are implemented.
