In the USA, setting the altimeter passing 18,000ft is fine as it's well into the enroute climb phase of the flight or fairly early in the descent phase. But when in the UK or even Europe, we have a mix of TAs ranging from 3000ft, 4000ft, 5000ft , 6000ft etc. This is puts the altimeter setting into a busy part of the flight. Is there any reason that the European airspace couldn't harmonise on a common TA of say 10,000ft which would coincide with the 10,000ft checks that our company uses and removes any possible confusion as to what the TA is at a particular airport during a high workload part of the flight?