IMHO...ATC should be aware that a clearence containing only "go direct" when executed by the pilots will cause the aircraft to turn the shortest possible way to the new fix.
Computer logic.
The turn left or right may not be the turn atc expect or want for various reasons.
It is wise to preceed the go direct with the required direction of the turn you require or as you said a turn left or right as you require to a heading pointing at the fix or very nearly so then the direct.
This atc awareness of the computer logic to go direct by the shortest possible turn is also relevent to departure aircraft go directs.
I recall CDG departure on 27R with a go direct clearence at 700ft caused the aircraft to turn left when what the the french atc chap wanted was a right turn out as per the sid then a direct, but he did not say so.
Such was ATC surprise as the aircraft climbed out left over the other runways it is said atc spoke in English for a full five minutes after the incident.
Being pissed off and french they then filed a violation against the captain which was defeated. But the conclusion was ATC CDG expected all turns to be right out of 27R.
CDG had another trick of clearing an aircraft for an Ils and switching the ils to the other runway when the aircraft was around 100 feet agl.
This caused pilots on a practice auto land to awake in a hurray as the aircraft lost the ils signal.
In this case the crew had not told the ATC they were doing a practice auto land, next time they did several times and atc also advised before they would swich over the ils.
IMHO...Out of hours direct communication between pilots and atc is one of the best safety features pprune and the internet provides.
They chances of everyone seeing eye to eye in the common market is....??
