I've thought of this before but it just seems like it would be incredibly easy to see by helicopter. Maybe spray painting the wood the same shade of green that the tree tops are would help disguise it.
i had the smae i dea tryed it it dont work very well man specialy when the tree strat to shake and have u ever tryed hicking up a 7 gallon pot filled with dirt up a tree not fun even with the soil fully dried out it was still a pain