peaks would be climbing and I would do 2 ladders on the straights with a guy on the ground moving ladders from left to right and to next straight while roof guy is climbing the peaks. bulb/clip all on ground in one long run, caps in fanny pack of roof guy for cutbacks, and set vampire plug in middle gutter downspout wherever outlet is near for cord drop. if c-9's only, my 2 best guys could do both jobs in a 8 hour day with a lunch thrown in there. but we probably would be doing wreaths, garland and mini's as well at least at one of the houses, so that adds time.
You could harness the heavier guy on the top ridge of the roof to the lighter guy that does the clipping, but why? Timewise makes no sense, and more dangerous than one guy on ladder and one guy on ground moving ladders to keep the guy on ladders moving. and I don't do this or reccomend this, more danger and roof damage, but here Christmas Decor uses the rooftop inverted "V" anchor on the top ridge. You can buy them at Lowe's for around 50 bucks, and it reccomends 8-16 screws on each side depending on climber's weight. I just can't think about that many holes in a roof year after year, even if you seal it with silicone.
2 year contract, auto renewable, I would charge the same per foot for both, 6.50 per foot the first year and 3.25 per foot in year 2, 3, etc. probably a slight price increase in year 4.