As you might know, the surge and drop of bitcoin in the latest Days, and the volatility, is mainly because the txfee. Its just not resonable to pay like 20 USD to send a bitcoin transaction just because the value is so high.
Not really, though it is unreasonable. There are more factors affecting the price of Bitcoin than that.
Since the value is loosely pinned to the difficulty (higher difficulty = higher value), what about a txfee that is based on the inverse of difficulty?
Basically, a required txfee that is based on the inverse of the highest difficulty observed the latest 6 blocks, and clients will use a txfee that is calculated based on the inverse of the lowest of these 6 blocks.
This will gurantee that the txfee used in a transaction is always higher than required, and that the txfee follows the value (txfee drops when value become higher).
This also gives a opportunity to mine old blocks when value are rising (as old txfee's are more valueable as they are higher), and mine new blocks when value is dropping (as these have higher txfee)
The target of a block is very heavily dependent on luck. The miners are randomly hashing the block header, with the nonce inside and generate new strings every single time. Every time they generate a block, they could just borderline meet the target or exceed it. Miners would never judge whether to mine or not, based on the past few blocks; they only do so via the difficulty adjustment. What do you mean by new and old blocks?
Txfee isn't defined by the network. The miner chooses the transaction and naturally, also sets a standard for the transaction fee.