Interesting question

Depends on what they mean by trough. The plants can get quite tall and if there isn't enough soil for roots, then they risk the plants simply falling out of the soil in high wind. I found that I actually had to 'fence' mine in to keep them off other plants as they'd grown very tall and heavy with beans. I might have been a bit heavy handed with the chicken poo but the plants sure loved it and cropped endlessly.

Most things will grow in containers provided you can provide the right soil conditions to support them, usually you would expect to need higher nutrient levels in a restricted root run to allow for maximum potential. So yes if the troughs big enough with good enough soil then yes go for it sell them a big trough too 

Thankyou for your answers.  As they have never grown anything before I think I will tell them no as they will not have any experience regarding feeding etc. The troughs we sell are only about 8 inches deep and although I will now probably lose out on a sale would rather do that than sell something to get a sale and then it all go belly up and get the blame. That's the reason we never recommend decorators or handymen when customers ask us because if it goes wrong they remember who recommended them not the person who did the job.