ditch it and get some nice easy access new upvc jobs all in a line - why struggle on an under priced, ball ache of an irregular job....
No, I would have a go, but I would manage the customers expectations. I would explain about the frames causing problems; that there will be spots and runs. I would even offer to touch up the ground floor windows by hand - even if this meant using an A-Frame.
But I still would put in a good price for the job, and if it was refused; hey ho!