Ethereum-based tokens are intrinsically bound to Ethereum. Any token transaction would be in the form of a valid Ethereum transaction, in a block on the Ethereum chain. (see footnote)
It's entirely possible, as you've seen, to reward miners in a token for including a token-related transaction. This would indeed probably require modifying mining software, although in a future where tokens are common this might become a default setting. Either way, a token miner would also be an Ethereum miner. There'd be no way to mine only the tokens--nor, really, would there be any reason when you could get 5+ ETH per mined block for no extra effort.
At the moment, token transactions are payed for in ETH, which any miner would accept. The problem with paying solely in tokens is that even if someone will include the transaction, no unmodified miner would. That's why, as far as I know, there are no token-based fees currently in common use.
Footnote: An Ethereum smart contract could host a sidechain, and then the sidechain would have its own kind of miner. That said, sidechains have less use in Ethereum, since you can write contracts to have most sidechain features.
Yes, ERC-20 tokens can be listed on various exchanges and they already do.
They need to be explicitly listed and some exchanges will ask money upfront.
At the moment, wallets maintain internal list of token names and contract addresses, and each wallet must be updated separately to display your token.
Best Answer
You can easily make new currencies on Ethereum by following the ERC 20 standard. If you follow this standard, other applications and people can easily interact with your token. This standard makes it very easy for people to read the total supply of the token. They simply call the
totalSupply()function. Often the creator of these currencies starts out with the total supply of the currency on his own account and he can then attempt to start an economy by distributing his token or by promising to back them up with an asset that he owns.Regarding mining: Are you sure you want mining as part of your token? Ethereum and Bitcoin gives the miners the native currency of the blockchain (ether/bitcoin) in order to incentivize them to secure the system by using their computing power. You do not need to secure your system since it is already secured as the rest of the Ethereum network.
See also: Once I have created my new Crypto Currency, how may miners mine for my currency?