Effectively you would be extending the second segment from 400ft to 1000ft. Then the third segment would be starting at 1000ft and the final segment would only be a 500ft climb to 1500ft.
All the net take-off flight path data in the analysis would be invalid. However, it would be relatively simple (if time consuming) to construct a new TOFP using the revised accel height, provided one had access to the performance charts for each segment (try the AFM).
In general terms. clearance over a close-in obstacle would be improved. whereas that over a distant obstacle would be worse.
At high elevations. time limits for Take-off Thrust may become limiting if the higher accel height was used.