What would be the consequences to lower the difficulty such that a block is generated every 5 minutes? The difficulty is adjusted such that a block is generated every 10 minutes.

What would be the consequences to lower the difficulty such that a block is generated every 5 minutes?
The most important consequence:

It would increase the orphan rate, which gives big miners more chance to mine (because they run their own ISP, while a miner with 0.1% hashrate of the network probably doesn't), and this leads to centralization.