Yes, you are right about these other parameters as liquidity, fungibility, durability, how easy is to use, security, privacy. There are critical "points of power" of BTC.
But there are many initiatives on the market like "colored coins", Mastercoin, Ethereum as“Bitcoin 2.0″ protocols – alternative cryptographic networks that are inspired by Bitcoin, but which intend to make the underlying technology usable for far more than just currency. They are allowing users to create their own currencies on the Bitcoin network, and more advanced protocols like Mastercoin, Bitshares and Counterparty which intend to provide features such as financial derivatives, savings wallets and decentralized exchange.
So potentially there is no technical ban to issue gigantic amount of virtual money to the market "sitting in Bitcoin" as a fully "spare" coins to BTC. Any of these coins will argument that is a bitcoin practically, and will use the factors of liquidity, fungibility, durability, etc. from the bitcoin network.
What do you think - will be changed approximated BTC inflation by these facts of issuing of any (fully-integrated-with-Bitcoin) new coins? From the economic theory if there is more money on the market then inflation will growth? Bitcoin will be in the same amount on market, but probably will be big amount bitcoin derivatives e.g. BitCoin2 working in the same Bitcoin wallet, fully exchanged to Bitcoin in decentralize way and offering him for example a premium by each bitcoin block.
What is your opinion?
There is no technical ban to issue whatever they want issue... but will people adopt, accept and use what they issue?
This is the point.
We already have Bitcoin as a generic payment system, why adopt another?
If Mastercoin or Bishares or others will build decentralized systems for financial derivates, futures, etc. what will be the user base of these? Who will start adopting them? What will be the advantage to move from Bitcoin and similar systems using bitcoins.
Ethereum use ethers. But Reggie Middleton's Ultra-Coin use bitcoins and the BTC's blockchain to do essentially the same derivatives/future stuff.
There is a huge value in using the same type of money as everyone else. There must be a gargantuan advantage to move to another (or a very tiny cost).
If any system/protocol built on top of bitcoin and using BTCs is able to deliver 90% of the value of any system built outside of BTC, people will naturally continue to gravitate around BTC.
This do not prevent the development or adoption of new cryptos, it will just relegate them to niches where they deliver absolutes advantages for specific applications.
Every improvement created outside of Bitcoin will be ported to Bitcoin if technically possible, just because there are too much wealth at stake the people invested in Bitcoin will fund developers to add these to Bitcoin.
A few years ago we had 3D web browsers developed. Now we use the same 2D browsers and if we want 3D navigation we add a specific extension using open protocols.