Not really.

Doubling the block rate has no advantage over doubling the block size.

Changing the rate though does have impact on coin production and that would be seen as a bad thing to many and potentially cause a loss of faith in the currency.

It also would decrease the difficulty in finding a block which has some other implications, some double spend attacks are only possible if you find a block first but don't release it before pulling off your double spend attack.

It's not clear what you mean.

There are currently an infinite number of blocks allowed by the protocol.  If you double that, you still have an infinite amount allowed.  There isn't any increase.

I assume that you mean to change the difficulty adjustment so that the average time between blocks is 5 minutes instead of 10 minutes.  This would also be a hard fork, since nodes that run the new software would accept blocks with an easier hash target than nodes with the old software.  Additionally, this isn't a long term solution.  Eventually, the transaction volume would grow to be more than double what it is today, and you'd need another hard fork (to increase block size? To cut the average time between blocks again?  Some other solution?).  That would mean we'd have to have this whole debate all over again with even more participants and even more newbies, and even more opinions, and even more risk (since the bitcoin economy would be twice as big as it currently is).

Furthermore, decreasing the average time between blocks would mean that orphan blocks would occur more frequently. It would also amplify the effects of delays between when a block is solved and when a miner hears about the solved block.  Miners that have slower connections (such as in China) would likely be against such a change.

If you didn't decrease the block subsidy and increase the number of blocks between halvings at the same time, then the remaining bitcoins to be created would be created in half the time.  This would be a significant change in inflation rate, and would be a difficult thing to get people to accept.

If you are properly set up, most transactions can be accepted with 0 confirmations.

Just make sure your client uses several well connected nodes for where it gets its transactions from, and do not accept incoming connections.

That makes the race attack very difficult because the transaction you see for a given input then likely becomes the same transaction the miners see and any double spend attempt will be rejected.

Most of the other double spend attacks require that the attacker be someone who has the hash rate to create blocks, and are very very hard to pull off - as in not worth trying for relatively small amounts of money.

The transaction confirmation problem really isn't one. Sure it may take hours sometimes for a given TX with a low fee to make it into the blockchain, but double spending on that TX is really hard unless you are a miner yourself. Even then it is hard.

But if you send it with a fee that small it will likely never get relayed to the vendor.

That's why as a vendor, your client should never accept direct connections - so that the double spender can't connect directly to your node to deliver the TX but instead has to get a TX that will get to the vendor by being relayed.

basically you want that bitcoin go in reverse trend and instead of an halving there will be a doubling, no sense

since two block every 10 mins, would be double the coins produced, also more dumping from miners that will be overwhelmed with a high profit

halving the difficulty and halving the reward is more complicated than just increasing the block limit buffer.

there are other ramifications too. such as reduced security because currently at the 10minute average some miners have the hash power/luck to make blocks in under 2 minutes. so halving the difficulty means that miners could with enough power/luck solve blocks even faster then that which opens up more risk of nefarious block creation.

there are other things that are affected with a halving of difficulty and reward, that are not affected by just increasing the blocksize limit buffer. so its much simpler to just increase the block limit buffer.

The difficulty adjusts based upon the current hash rate so that as the hash rate increases, so does the difficulty, to target 10 minutes.

Any individual block may take more or less time than the target, but on average it is about 10 minutes.

Well you could say that investors are aware of 1Mb blocks, so why mess around with that.

With regards to scalability - is a 10 minute limit the correct one to fix given the improvements in processing powerr and bandwidth. I looked at this page -

https://bitcoinwisdom.com/bitcoin/difficulty

and I noticed that the difficulty can decrease as well as increase. So should the difficulty be varied to cope with transaction rate, UTXO size or some other factor, rather than just compensating for increased computer power.

The pressure seems to come from the users rather thaan the miners.

On reflection, I'm still not sure why locking block creation to an average of 10 minutes is essential. It seems that it's possible to have a burst of blocks added to the chain, and the software seems to cope with that. A system with automatic scalability, would need to be orientated around the users far more than the miners. At the moment scalability seems to be based on political infighting and vested interests rather than software design.

well "users" are helped by the miners, the other supply is simply being matched against the demand, but it's the additional supply that is created that can lead to the dumping, and especially the manipulations done by the miners