It is perfectly acceptable to have different takeoff charts based on a VMC departure and a IMC departure.
The difference in obstacles is the width of the obstacle cone. On a straight out departure the IMC (normal RTOW chart) has a half width of 600 m. For VMC departures the obstacle cone may be reduced to a half width of 300m.
You CANT invent your performance... if u dont have an RTOW with VMC clearly stated on it. Then u MUST takeoff using the noraml RTOW chart.
If u lose an engine, it doesn't make an arse difference if u can see the obstacle as u fly into it. Its still going to hurt.
However if itd 600 meters to your left, and ther is nothing to your right, then in VMC conditions, it is perfectly allowable. And it is clearly stated in JAR OPS.
rgds
O\Z
rgds
O/Z