On the 737 and with the way our performance is set up any obstacle and engine failure between V1 and passing MSA is considered. To be safe during that time we have to stick to the calculated flap schedule which is based on heights. V2 + 20 can be up to 50kts below minimum clean speed, so pitching down to accelerate those 50kts upon reaching V2 +20 will immediately invalidate any obstacle clearance (not to mention any required NADP). The furthest obstacle considered I've seen was around 30NM from the departure end of he runway, our EFB tells us something like that just for information. Acceleration heights are usually different for all engines operating and one engine out, both have to be filled into the Take Off Ref page 2 during preflight, same as the thrust reduction height.