So you want to tell me that you don't know that a visual departure is not the same as an IFR departure (performancewise)?
Errm, yes? (Initially.) What does being able to see the trees at the end of the runway have to do with hitting them or not? If you haven't got the energy to clear them, you're going in, visual or not. WAT limits, anyone?
What do
you do when
you're flying - "it's a nice day, let's put on another 30T over RTOW"? I'm sure you don't. How is looking outside the cockpit going to help you during the 1st & 2nd segment climb? As asked before, how is being 'visual' improving terrain clearance when you're still inside the airfield boundary?
OK, if you are well clear of the ground in clear vis. you can manoeuvre to avoid obstacles and make your way back into the circuit. Bear in mind that 'terrain constrained' airfields often require quite precise navigation and speed control to avoid the cumulo-granitus. Places like Bogota and San Jose come to mind. If you set off down an unknown valley after an engine failure because it looks good, don't blame the performance engineers when you can't get out of the other end.
As soon as you take matters into your own hands and deviate from laid-down performance criteria, you are on your own. I agree in the obvious cases like completely flat terrain or taking off with a thousand miles of sea between you and the nearest obstruction that you can make some of it up as you go along. Anywhere else I would exercise extreme caution as the difference between an AEO and OEI departure can be like night and day - bearing in mind that most, if not all our experience has been AEO...